I had this issue with Android 10 and now on a new phone with Android 11.
I have the Power Saving mode turned on – and I have excluded my apps from power saving. So I thought I could keep PS turned on while still running apps that need GPS, so long as these apps were excluded from power saving plan.
But this does not appear to be the case:
This morning I went out for a 10K run. My app – SportActive – reported that it was not able to retrieve GPS data from Android, and suggested that I turn off power saving.
So I switched off Power Saving and Adaptive Battery.