Hey Dennis, sounds like you’ve covered most of the basics. A few things to check: make sure the antenna switch (INT/EXT) is physically set correctly on the module. Also, the NEO-M8N can take a few minutes for a cold start—try leaving it powered outside for 15–20 minutes. Lastly, ensure it has a clean 3.3V power source; voltage drops can affect satellite acquisition. If none of that helps, try updating the GPS firmware via u-center. Two dead modules is unlikely, but not impossible. Good luck!