I can't get Pilot2atc flight plan to transfer to the sim. I have connected, and I have turned off many of the features in MSFS 2020. In addition, I can't get the "on top" feature to turn on. Thoughts?

I have moved your topic to the appropriate forum.

It doesn't transfer automatically.  You have to export it to the MSFS format and then load it into MSFS using the Load Flight Plan function in MSFS's Flight Plan (World) window.

Dave

Dave, Thank you! I will try and see if it works. Speaking of not working, will your solution also address the on top issue?

On-Top can only work if the SIM is running in Windowed mode because if in "Full Screen" mode, Windows does not control the graphics at all and cannot keep P2A on top.  

Thak you. Also, the radio stack feature onnly partially works. I can enter frequencies for nav but I can't for com. Will your solutio9n address this issue? Thank you for your advise!

If you can't change the Com Frequencies in your aircraft, then there is a problem with the SIM or the aircraft.

If the freq is changing by itself, you may have one of the ATC options set wrong.  Try disabling MSFS ATC as follows:

Options -> Assistance->Piloting->AI Radio Communications (ATC) - OFF
Options -> Assistance->Navigation Aids->Route & Waypoints - OFF
Options -> Assistance->Navigation Aids->Taxi Ribbon = OFF
Options -> Assistance->Navigation Aids->Landing Path - OFF
Options -> Assistance->User Experience->ATC UI Panel Open at Start - OFF
Options -> Assistance->User Experience->Show Message Log in ATC Menu- OFF
Options -> Assistance->User Experience->ATC Voices - OFF
 

Some aircraft don't allow external programs to change frequencies, and if so, you would have to change the freq in the cockpit instead of using P2A.

Dave