I have been running a 1280 series 1 APM board and have just upgraded to a 2560 APM 1 board.
I load v2.3 of Arduplane via the Mission Planner (1.1.55) and set up the radio, compass etc.
The GPS light comes on indicating lock but only LED B lights on the Oilpan (showing Home position not set?). If I go into CLI mode and do Test/GPS then the C LED comes on and I get correct GPS data displayed for my position. The Status display in the Mission Planner seems to show everything is OK except the Long/Lat is not displayed although the time and date is displayed. The HUD shows 'No GPS'.
I have reloaded v2.3 but no change.
I have not experienced this with the 1280 board and the Oilpan has been transferred across.