Motors stopped spinning when armed, after radio calibration

I have an F550 copy with APM 2.6. I love it and have got used to stabilize before going onto altitude hold, loiter etc. I am using Flysky FS-T6 transmitter. (just got telemetry kit but haven’t flown with it yet). I am using APM Planner 2.0.15.

I recently recalibrated the radio while trying to get the switches to change flight modes- which works as expected, but I seem to have caused the motors to stop spinning upon arming. I didn’t realize this to start with which nearly caused me to crash the drone a few times as I hadn’t relized that it was armed.

What’s weird, is that the MOT_SPIN_ARMED parameter (?) is still set correctly, and it doesn’t look like the spin speed has been set.

What could be causing this? Additionally- I can’t figure out whether I should have channel 2 on reverse or not- does anybody who flies this model have CH2 reversed? It’s in X configuration.

Also, when I upgraded APM planner all the buttons had disappeared, so I had to downgrade. Anybody else experience that with 2.017?