The GPS may sometimes be imprecise if you're inside a building. Therefore, if your phone's GPS cannot collect the location and you are unable to start or finish your shift, here's what you should do:
1. Go to Settings → Location Settings → Increase Accuracy. (Additionally, turn on WiFi if possible - turning on WiFi makes the GPS find the location faster).
2. Go to your phone's settings → Apps → Calamari:
Make sure our app has permission to access the location in 'always' mode
Make sure Calamari has permission to use background data
Make sure the Calamari app has battery optimization disabled
More information
If you still need help, please try solutions from Google. You can contact them here.