A few suggestions:
1. Does the
NMEA debug window also show NMEA-sentences coming in? (adding a screenshot might be useful for us to help you).
2. Give the GNSS-receiver plenty of time (10 minutes or so) to get a fix and make sure the receiver has an unobstructed 'view' to the sky (preferably out in the open air, so not indoors).
3. In Dashboard, add 'GNSS Status' so that you can see if -and how many- satellites are found and if the signal-strength is sufficient.