APM 2.6 telem1 port not working?

HI, I just recieved a new APM 2.6 and soon I realised it’s telemetry port doesn’t work. I tried the same setup on different APM and it worked, So I opened the faulty APM and all the connections were I think OK. What should I do? I tried enabling the telemetry in optional hardware, but no succses.

Im using AP 3.4.


I think that this may be the answer to your problem with your APM2.6:

APM 2.6 - no longer supported for Copter or Plane. The last firmware builds that fit on this board are Copter 3.2.1 and Plane 3.3.0.