The GPS may be sometimes imprecise if you're inside of 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:
- Go to the Settings of your phone
- Find Location settings
- Go to the Mode and select 'High accuracy'
More information
If you still need help, please try solutions from Google:
https://support.google.com/maps/answer/2839911?co=GENIE.Platform%3DAndroid&hl=en