Apple warned customers who still have an iPhone 5 to update the device by 12 AM UTC on November 3, 2019. Not doing so will mean key functions like GPS App Store, iCloud, email, and web browsing will stop working properly.
Update iOS on iPhone 5
Apple also warned:
If the update to iPhone 5 is not completed by November 3, 2019, you will be required to back up and restore using a Mac or PC in order to update because over-the-air software updates and iCloud Backup will not work.
The correct version of the iOS the device should be running is 10.3.4.