It happens to students even at home and hotspot at school.
I ran across something interesting yesterday - My original setting for "DeviceShowUserNameOnSigin" was set to "never show user names & photos." If I change that to "always show user names and photos," I cannot replicate the errors after trying 10 plus times to log on. Once I change it back to "never show user names & photos" and tried to log in, I immediately got the "you are not authorized to use this device:" error. Reported to Google...their response: t has to do something with the User data that gives you guys the Error & they will research.