500 type don´t ring

[tyro03]

Hi everyone:
There´s a DN which don´t ring, that´s the problem, I connect it to another wall jack, I dial to this new DN.. and it rings, so the telephone is working. Now, what could be the problem, how can a proble like this happen suddenly..
Once I know someone is calling I pickup the handset and answer the phone, but because I was making test and ask a friend to callme back and answer the phone and it worked, I received the call, but without a ring...

I´ve heard something about change the port, can someone tell me what is this about...?

Thanks in advanced...

 

[McGruff753]

Post the TN's for both the non working and the working TN's. Thanks.

 

[phonejack99]

Make sure that the IPE shelf of the non working/ringing phone has a ring generator installed in it.