If you turned off the GPSM or disconnected it, put it back. Some versions of the IPC’s for 2015 (early models) will rely on the old modules still in place for the IPC compass. It’s the same on 2015 F-150’s.
You should understand that the GPS system in the APIM has nothing to do with the APIM firmware, other than passing location info to the Sync app. This is a separate subsystem of the APIM module, just as the NAV and Sync systems are separate systems. They only interact, with Sync being the human interface.
That said, you should try to troubleshoot the basic hardware first. GPS Hardware Test: The Compass/Navigation is Inoperative or Does Not Operate Correctly. (No GPS)