BIG Offtopic - Fritzbox 7490 and external Fax

Hey guys,

sorry for this big offtopic, but i’ve got a pretty big issue with one of my clients:

They had a phone system which i disconnected because they stopped working with the company that set this up for them (we dont have access to it).

Now, we use 3 phones (fritz!fon) with the already set up fritzbox 7490. The printer is a Utax 302ci. Internet and Phone Connection is via DSL. Everything works fine, except Fax. The Printer/Fax device is connected via Fon1 (for fax) and via Lan (For printing etc.). The phones work perfect, but we cant receive or send fax anymore.

I have tried disabling T.38 protocoll, set up the fax again, restarted the fritzbox, used the landline option with the fax-switch option. None of these works. The weird thing is: The Printer seems to receive something, but wont print anything (which has worked before).

Is there a pro online that might have stumbled over this issue aswell?

Thanks in advance!