Gps does not work in my application after installing Mestastic

Hi @eb4cuv, welcome to the community! Odd that switching between firmware changes the GPS behavior.

For your software do you use the UBX protocol or NMEA? Meshtastic prefers UBX so it is possible there is some config that happens that disables NMEA (I haven’t checked).

You could try reset to factory using serial pass through and U Center. There is some good info here "No Sats" status on Oled although this hasn’t been used for the v07 tbeam.