I cannot get my Vtech LS6204 to register. I have tried everything and the screen always reads registration failed.

Add and register a handset
Each newly purchased handset must be registered to the telephone base before use. When first purchased, each expansion handset shows NOT REGISTERED.
You may need to charge the phone first.
To register a handset:

·Place the unregistered handset in the telephone base or charger. Press Find for 4 seconds. If the headset screen doesn't light up after the 4 seconds. You will need to charge it some more.
·After making sure it is charged set the telephone on the main base again press and hold the Find button for 4 seconds ( until the red light IN USE comes on) Then release the find button. The headset will show PLEASE WAIT; this takes about 10 seconds to complete the registration. The hand set will show HEADSET REGISTERED and the headset number assigned, you will hear a beep when the registration is finished
·When the registration is complete, the newly registered handset is assigned the next available handset registration number. For instance, if you already have HANDSET 1 and HANDSET 2, the next registered handset is HANDSET 3.
·Makes sure no other headsets are in use at the time or the registration may fail.
·You cannot register a handset if any other system handset is in use. Only one handset can be registered at a time.

This sounds like a registration problem, the handset(s)
and the base have lost identification with each other.

I. To address this, first de-register the handset(s) ---
do this procedure for each handset:

0. Start by taking off the battery compartment cover....

1. press [menu]
2. scroll up/down to "Settings"
3. enter * 7 8 9 0 #
4. scroll down to "next page", press [select]
5. scroll down to "Register Clear?", press [select]
6. display asks "Confirm?" or "Register Clear??", press [select]
7. display reads "Ok" and chirps, press [ off ]

8. UNPLUG THE HANDSET BATTERY (why the cover was off)

9. Wait ~30 seconds, re-connect the battery & replace the cover

10. display reads "Not Registered" ===============================

II. To register the handset to the base:

1. press [Find Handset] on the base and hold for
~4 sec until the "In Use" lamp lights.
2. press # on the handset and set the handset into
the handset cradle on the base
3. within 30 seconds or so, the handset will either
chirp and display "Handset Registered", then
"Handset #1" or it will say "Registration Failed".

NOTE: the battery must be well charged prior to the
registration process, a weak battery may cause a
"Registration Failed". Charge the battery for a few
hours and try the registration ( II ) again.

NOTE: the base can only handle 5 handsets and will
increment the number of each handset registered
until "Handset #5" has appeared, even if some of
the handsets are lost/not in use. Trying to register
more than 5 handsets will result in "Registration Failed."
===============================

III. To clear the base of all handset registrations and
be able to start registering again at Handset #1:

1. press [Find Handset] on the base and hold past ~4 sec when the "In Use" lamp lights, at
about 10 secs the "In Use" lamp will begin to
blink.
2. release the [Find Handset] button momentarily,
then briefly press it again. After a moment,
all handsets that were registered to the base
(if any) will display "Not Registered" and be
ready for fresh registration
3. for multiple handsets, return to II. above and
register each handset in turn.
===============================
Good luck !!

This sounds like a registration problem, each 'old'
handset must be de-registered from its original
base and then registered to the 'new' base.

NOTE: the CS6229 handles a maximum of 5
handsets. If you have a handset displaying
"Handset #5" then you have a 'fully populated system'
even if you actually have only one or two handsets.

You will need to clear each handset ( I ) then clear
the base of all registrations ( II ) before re-registering
each handset ( III ) up to the maximum of five.
=====================================
( I ). First, to de-register a handset ---

0. Start by taking off the battery compartment cover.

1. press [menu]
2. scroll up/down to "Settings"
3. enter * 7 8 9 0 #
4. scroll down to "next page", press [select]
5. scroll down to "Register Clear?", press [select]
6. display asks "Confirm?" or "Register Clear??",
press [select]
7. display reads "Ok" and chirps, press [ off ]

8. UNPLUG THE HANDSET BATTERY
(this is why the cover was off)

9. Wait ~30 seconds, re-connect the battery &
replace the cover

10. display reads "Not Registered"
===============================

( II.) To clear the base of all handset registrations
( if needed, else skip ahead to ( III ). )

1. press [Find Handset] on the base and hold
past ~4 sec when the "In Use" lamp lights, at
about 10 secs the "In Use" lamp will begin to
blink. 2. release the [Find Handset] button momentarily,
then briefly press it again. After a moment,
all handsets that were registered to the base
(if any) will display "Not Registered" and be
ready for fresh registration ===============================

( III.) To register each handset to the base:

1. press [Find Handset] on the base and hold for
~4 sec until the "In Use" lamp lights.
2. press # on the handset and set the handset into
the handset cradle on the base
3. within 30 seconds or so, the handset will either
chirp and display "Handset Registered", then
"Handset #x" or it will say "Registration Failed".

NOTE: the battery must be well charged prior to the
registration process, a weak battery may cause a
"Registration Failed". Charge the battery for a
few hours and try the registration ( III ) again.

===============================
Good luck !!

The errant handsets must be de-registered from their
original base and then registered to your base.

NOTE: the CS6649 handles a maximum of only five
handsets. If you have a handset displaying
"Handset #5" then you have a 'fully populated system'
even if you actually have only one or two handsets.
In that case, you can clear each handset ( I ) then clear
the base of all registrations ( II ) before re-registering
each handset ( III ) up to the maximum of five.
=====================================
( I ). First, to de-register a handset ---

0. Start by taking off the battery compartment cover.

1. press [menu]
2. scroll up/down to "Settings"
3. enter * 7 8 9 0 #
4. scroll down to "next page", press [select]
5. scroll down to "Register Clear?", press [select]
6. display asks "Confirm?" or "Register Clear??",
press [select]
7. display reads "Ok" and chirps, press [ off ]

8. UNPLUG THE HANDSET BATTERY
(this is why the cover was off)

9. Wait ~30 seconds, re-connect the battery &
replace the cover

10. display reads "Not Registered"
===============================

( II.) To clear the base of all handset registrations
( if needed, else skip ahead to ( III ). )

1. press [Find Handset] on the base and hold
past ~4 sec when the "In Use" lamp lights, at
about 10 secs the "In Use" lamp will begin to
blink. 2. release the [Find Handset] button momentarily,
then briefly press it again. After a moment,
all handsets that were registered to the base
(if any) will display "Not Registered" and be
ready for fresh registration ===============================

( III.) To register each handset to the base:

1. press [Find Handset] on the base and hold for
~4 sec until the "In Use" lamp lights.
2. press # on the handset and set the handset into
the handset cradle on the base
3. within 30 seconds or so, the handset will either
chirp and display "Handset Registered", then
"Handset #x" or it will say "Registration Failed".

NOTE: the battery must be well charged prior to the
registration process, a weak battery may cause a
"Registration Failed". Charge the battery for a
few hours and try the registration ( III ) again.

===============================
Good luck !!

"Register" refers to the pairing of the handset to
the base so they can communicate securely
in private via an encryption scheme so no one
can easily evesdrop.

When you first set the phone up for use, you will
need to effect the registration then:

( III.) To register each handset to the base:

1. press [Find Handset] on the base and hold for
~4 sec until the "In Use" lamp lights.
2. press # on the handset and set the handset into
the handset cradle on the base
3. within 30 seconds or so, the handset will either
chirp and display "Handset Registered", then
"Handset #x" or it will say "Registration Failed".

NOTE: the battery must be well charged prior to the
registration process, a weak battery may cause a
"Registration Failed". Charge the battery for a
few hours and try the registration ( III ) again.

===============================
Good luck !!

Follow the instructions on page 43 of the manual: http://cdn-media.vtechphones.com/media/p/document2/products/%7B4B5F2951-48EE-413C-9CAF-3F956892A909%7D/CS6719-2_UM_2.pdf

Normally you just drop the expansion handset into the charger of the master & the phone will be registered automatically.

Yes. The'old' handset must be de-registered from its
original base and then registered to your base.

NOTE: the CS6229 handles a maximum of 5
handsets. If you have a handset displaying
"Handset #5" then you have a 'fully populated system'
even if you actually have only one or two handsets.

You will need to clear each handset ( I ) then clear
the base of all registrations ( II ) before re-registering
each handset ( III ) up to the maximum of five.
=====================================
( I ). First, to de-register a handset ---

0. Start by taking off the battery compartment cover.

1. press [menu]
2. scroll up/down to "Settings"
3. enter * 7 8 9 0 #
4. scroll down to "next page", press [select]
5. scroll down to "Register Clear?", press [select]
6. display asks "Confirm?" or "Register Clear??",
press [select]
7. display reads "Ok" and chirps, press [ off ]

8. UNPLUG THE HANDSET BATTERY
(this is why the cover was off)

9. Wait ~30 seconds, re-connect the battery &
replace the cover

10. display reads "Not Registered"
===============================

( II.) To clear the base of all handset registrations
( if needed, else skip ahead to ( III ). )

1. press [Find Handset] on the base and hold
past ~4 sec when the "In Use" lamp lights, at
about 10 secs the "In Use" lamp will begin to
blink. 2. release the [Find Handset] button momentarily,
then briefly press it again. After a moment,
all handsets that were registered to the base
(if any) will display "Not Registered" and be
ready for fresh registration ===============================

( III.) To register each handset to the base:

1. press [Find Handset] on the base and hold for
~4 sec until the "In Use" lamp lights.
2. press # on the handset and set the handset into
the handset cradle on the base
3. within 30 seconds or so, the handset will either
chirp and display "Handset Registered", then
"Handset #x" or it will say "Registration Failed".

NOTE: the battery must be well charged prior to the
registration process, a weak battery may cause a
"Registration Failed". Charge the battery for a
few hours and try the registration ( III ) again.

===============================
Good luck !! --

the accessory hand sets have to be vthech ls5475 units the same as what came in the original packaging
the extras you got will not register with an incorrect base
take them back and exchange for the correct units