I have received my APM2.5 this week and have downloaded MP and had a play. I interfaced to my RC controller in preparation for a flight.
I have set up all the channels as recommended and flicking switches on the radio changes the APM's modes to manual/auto/RTL as expected. Also, in these modes, I can see the control surfaces moving, so almost everything is OK!
But.... in the Config>>Failsafe section I can see that APM does not want to control throttle. It won't bump the throttle and at all times it sits at zero. I'm in armed mode. Not sure what else to check or enable?