"Silly question for you, did you power your servos with a ubec? The apm 3.1 only sends a signal and not power. You need to power your servos"

"A quick question for you. Are you using pwm or s.bus? S.bus will allow you access the addressable channels."

"Check your solder connections on the apm board. I picked up am apm2.8 and couldn't get telemetry or arming to work. I looked at the bottom of the board and found no less than ten bad solder connection. A lot of them bridged pins. You'll need a…"

"Also, try resetting the minimosd on the minimosd as well as in mission planner."