Sometimes your phone will have trouble finding a GPS signal and you will not be able to take images. If you have bad GPS signal, try to move a bit and get away from tall buildings. If that doesn’t work, restart your phone and see if that helps.
Bad GPS fix—the capture button to the right is disabled
By default the GMS (Google Mobile Services) are disabled in the Android app—this is to encourage people to start taking pictures outside. But enabling GMS might improve your overall GPS fix. To enable GMS, please go into settings, choose the Developer section and enable “Use Google Mobile Services”—this will enable location fix from several sources.
You can also consider choosing the “Skip location check” option in the app settings (in the Developer section), which will let you capture without a GPS fix, but pay attention that you then later need to fix the GPS coordinates manually on your computer in order to upload the images onto the map. If you are recording a GPX track with an external, more powerful device, you can also use that to geotag the images.