Reset all outdoor activities to GPS+GLONASS is the only fix for this I can find. Maps present in Sept 2019 went missing after the 14.20 update for Fenix 5. I did get a very quick reply from Garmin to re-sync using Express and then delete all my activities on my watch, which I did but to no avail. All history is still maintained on Garmin Connect and Strava, so its no loss to clear the watch. HOWEVER, after resetting all outdoor activities on my Fenix 5 to use both GPS+GLONASS, its working again!