One line is always in use

Do name/number display on any other phones on that line?

If that is your only phone, try borrowing another with working call display from a friend or neighbor. If another phone doesn't display caller info, call your phone company - most charge extra to provide caller number ( and in some cases, another extra to add the name). Even if the features are included in your rate, it's possible they weren't turned on correctly.

Your Panasonic may also have a setting to show name or number - depending on the display size, you may have to pick one or the other.

Finally, some phones do not support exactly the same caller ID info that the phone company sends - I have seen some which displayed number instead of names and no name, just because the two pieces of equipment did not agree on the standard. Try your Panasonic on someone else's line with working Caller ID.

First, lets get rid of the static. Try Feature #86. This will turn off background music. When a music source is not attached you get static.

Enter programming by using Feature XXX66344 password 266344. The display should show "Terminals&Sets" press the top right button with an indicator in the display. The display should show "Show set: ____ enter the extension number that you want to check or program. The display will show ***:name. Press the top right button three times. The display will show Show Line:____ with options to Scan or List. If you select Scan it will show the lines assigned to that phone. If you select List it will start with the first line in your phone system showing one of four states 1- Unassigned, 2- Ring Only, 3- Appear&Ring, 4- Appear only. Change the selection on the line by using the CHNG soft button. This is where line assignments are changed from the four states for each extension.

The only other thing that will keep an extension from ringing is "Do Not Disturb" or DND. Feature 85 and #85 will turn this feature on and Off.

The phone line is supplying a certain amount of power. If you open many parallel channels the power is distributed among active phones. The more sets there are the less power each one gets.These are the physical principles behind the limitations on the number of ringers a single line can activate (Ringer Equivalence Number)
As to the need to be using 3 or more sets on the same line and at the same time, I have a hard time understanding that.
For a landline, your phone company can activate 2 numbers, as it can enable A/DSL on your phone line.

When you press PROGRAM and CO4, what does the display say? A Panasonic TA series system starts with 3 lines. If you're trying to access line 4 and you don't have it, you might get that display, or line 4's button may be assigned to something else. Last, try unplugging the phone system cabinet and plugging it back in. That will reset all calls.

Carl

Programming is done on M7310, M7324 and T7316 sets.
To set up ringing you need to enter programming by pressing the feature key followed by **266344.When prompted to enter the password enter 266344.
The screen should say TERMINALS&SETS. The 4 top line/feature keys are now used for programming.
At the terminals&sets prompt, press the show key (top right arrow). The display should now ask for an extension number. Enter extension number you wish to program ringing on. Press the show key (top right arrow)
The display should sat LINE ACCESS
Press the show key (top right arrow) .
The display should say LINE ASSIGNMENT.
Press the show key (top right arrow) .
The display ask for a line number. press list
The display should say line 001: appear only
press the Chng key til it says appear and ring
press next key (lower right arrow)
The display should say line 002: appear only
press the Chng key till it says appear & ring
Continue til all of your active lines say appear and ring
press the heading key(top left arrow) till the display asks for another extension number
repeat line programming for that extension
press the release key when finished

Programming is done on M7310, M7324 and T7316 sets.
To set up ringing you need to enter programming by pressing the feature key followed by **266344.

When prompted to enter the password enter 266344.
The screen should say TERMINALS&SETS. The 4 top line/feature keys are now used for programming.

At the terminals&sets prompt, press the show key (top right arrow).
The display should now ask for an extension number.
Enter extension number you wish to program OLI on.
Press the show key (top right arrow)
The display should sat LINE ACCESS
Press the show key (top right arrow) .
The display should say LINE ASSIGNMENT.
Press the next key 5 times (bottom right arrow) .
The display should say OLI #.
Press the Chng key and enter in your DID number,
Press ok when finished.
Press the release key when done programming.

First, you'll have to know what the line number is in the system for the new line.
To get the line port number, on the set/s that the new line appears on press feature *0 and the the new line.
The display should say for example L025:LINE 05.
The port number of the example is port 025.
write the port number of the new line down for future reference.
Programming is done on M7310, M7324 and T7316 sets.
To set up ringing you need to enter programming by pressing the feature key followed by **266344.When prompted to enter the password enter 266344.
The screen should say TERMINALS&SETS. The 4 top line/feature keys are now used for programming.
At the terminals&sets prompt, press the show key (top right arrow). The display should now ask for an extension number. Enter extension number you wish to program ringing on. Press the show key (top right arrow)
The display should sat LINE ACCESS
Press the show key (top right arrow) .
The display should say LINE ASSIGNMENT.
Press the show key (top right arrow) .
The display ask for a line number. press list
The display should say line 001: appear& ring
press next key (lower right arrow)til you see the line port number you wish to program
The display should say line 0xx: appear only
press the Chng key till it says appear & ring

press the release key when finished

When a phone has only 2 lines, it's not programmed. By default, a Nortel system has 2 lines and that's all. Go into system programming and assign the number of lines and intercoms to a phone. After that, you can copy the buttons from a working phone to the new phone and you're done.


Carl

First, check your fax's phone line. Put a regular phone on it and check for dial tone and line noise. If the line is dead or noisy, this will cause a problem. 
You can also try dialing your fax number from another phone and see if the fax unit picks up the line and starts initiating communication. (sounds like modem noises)