After several sim updates, the exact location of your Community folder may have changed. To find out its present location, activate Developers Mode within the MSFS settings. A small toolbar will appear on top of your screen. Select the "Tools" tab, then select Virtual File Sytem. Here you will be able to see the location of both your Official folder as well as your Community folder as used by MSFS (see screenshots).
About the A310 other issues: as a general trick, always start aircraft with this level of complexity in "Cold and Dark" state. Before selecting the aircraft in the MSFS menu, make sure your gear lever is in "down" position, thrust levers in ïdle" position, speed brake and flaps levers in "retracted" positions. Furthermore, throttle calibration is partially done outside MSFS, partially upon MSFS startup (recommended to create a dedicated profile for the A310 in the Control Options menu, and finally in the A310's EFB when the A310 is selected. On youtube, I have found many very useful video's explaining how to calibrate the A310's throttle.