Why cant i put my m7208 on hold or call out on any line

Most likely there is a button stuck somewhere.

here's a link/site I found hope tis your system
https://pbxbook.com/norstar/line.html

try another M7208 phone using the same connection including the same line cord, if that phone works then the first phone is bad, if not then look for trouble at the outlet or line cord

To turn off background music, press feature #86.

No, the M7208 is a propriatary set which requires the PBX to function, whereas the aastra phone is a stand alone set which requires a standard telephone line and a power source.

If you haven't already tried it, unplug the phone, press a couple of buttons, then plug it back in so it resets. If the boxes still appear, try adjusting the display contrast. Press Feature-*-7 to get to contrast setting and then press 6 or 7 to set mid-range contrast.

Here are the instructions for making a conference call on a Norstar system.

Conference [Feature] [3]

• Establish a conference call between yourself and two other parties.
  1. Make or answer the first call.
  2. Put the first call on hold.
  3. Make or answer the second call.
  4. After the second call is connected, press [Feature] [3].
  5. Press the line or intercom button of the first held call.
  6. Press [Rls] to end the conference call
• To remove yourself from a conference permanently (unsupervised conference):
  • Press [Feature] [7] [0]. The other two callers remain connected. (Some external lines may not support this feature.)
• To put a conference on hold:
  • Press [Hold]. The other two callers can still talk to each other.
• To split a conference:
  • Press the line or intercom button of one caller to consult privately while the other caller is on hold. To re-establish the conference, press [Feature] [3].
• To disconnect one party:
  • Press the line or intercom button of the caller you want to disconnect, then press [Rls].
  • Press the line or intercom button of the remaining caller to resume your conversation.
• To independently hold two calls:
  • Press the line or intercom button of the first caller, then press [Hold]. The second caller is automatically put on hold. To re-establish the conference, retrieve one call from hold, press [Feature] [3], then retrieve the second call from hold.

Increase the contrast of display of ur phone it might fix the problem

Make your first call, press hold. Make your second call (internal or external). Press the conference button, then the display will tell you to press the other line (the first one you put on hold).

Your Nortel M7208 phone is plugged into your Norstar phone system (not the phone line) You would not be able to use DSL on the same phone port used by the M7208 phone. A filter connected to that port would not solve a DSL issue and could only cause problems with the M7208 phone. You may need to put the filter on the phone lines before they connect to the Nortel phone system... I don't know which system you have or how it is wired up so I am not sure how easy that would be for you.