The pinout of the audio radio cable of the DigiRig and the Mobilinkd are different. If you use the same cable to connect to your radio, that's your problem.
I use my digirig cable with the Mobilinkd and this adapter too. Works
fine. If I change radios sometimes I have to change the PTT style from
Simplex to Multiplex and vice versa in the Mobilinkd config app.
The adapter should change the pinout to let the digirig cables work with
the Mobilinkd (TNC4).