USB with no mavlink / diagnostics

Greetings all.

I operate on a pixhawk px4 2.4.6 by 3DR., Rover Version 3.1.2

My situation is that i can get no MAVLINK running on USB and have a hard time to do firmware uploads. I do have telemety via TELEM1 / 3DR radio.

I came across this case: which seems plausible for my situation.
Like there it is my intention to connect via mavros.

I used mission planner to connect via 3DR radio to TELEM1, and am successfull accessing Terminal /nsh via Mavlink.
To my surprise though, the mavlink command is not available and not listed as a module in help.

  • How can i diagnose the USB / Mavlink ?
  • Does missing mavlink mean my firmware is incomplete ?
  • If things have changed, where can i find current documentation ?

Thanks for your support