Have had similar issue on ocassion, seems be whenever the gps is busy or stuck.
When that happens whatever the reason, the button to capture does nothing and merely flickers the pick resources button.
Only caught a couple gps fails so far: when i open in a fast vehicle (not driving!) and also when i minimize the app and reopen, likely poorman's phone fail.
Also, found google location doesnt work if wifi is off before data is turned on, must have it on first, for entirely obscure reasons.