Activate location for "Find my Device"

When I go to https://www.google.com/android/find?u=0 (Find my Device), it says "Online" and "Location Turned Off" (under the device name) and the device is not located on the map.

I have checked the following on the device:

• Settings->Security & Location->Find My Device: is "On"


• Settings->Security & Location->Location->Use Location: is "On"


• Wifi and mobile data are on (I have Internet connection)


• The device knows its location (in Google Maps)


• Find My Device can make my phone ring remotely.

Note: Sometimes the map shows the device (and the message becomes "Last seen ...") but this happens only rarely and under unpredictable circumstances (and a reload of the webpage makes it go back to "Location Turned Off" even if the phone was not moved and no settings were changed).

My device is an Umidigi A5 Pro with Android 9.