How do I de authorise a device?
Is this being done in High Sierra of Big Sur?
If in High Sierra open iTunes and iTunes account and find the device you what to De-authorize and remove it.
If in Big Sur >> open Music and same procedure as iTunes
This answer didn't help. I have the same question. It doesn't list devices, just gives the choice to authorize or deauthorize this computer. But it told me I have two computers authorized. How can I see what the other computer is? And do user accounts on the same computer count as separate authorized devices?
If you have access to each device, you can, on that device, open iTunes, go to the Accounts menu, go to Authorizations, and select Deauthorize This Device.
If you don't have access to the devices, you can from the iTunes Accounts menu, select View my Account, and deauthorize ALL devices for this account. The you can reauthorize the device(s) you want.
These are the only two options you have. Either deauthorize individual devices when logged in to those individual devices, or simply deauthorize all devices at once associated with the account.
Two user accounts on the same computer count as only one authorization -- it is by device.
I will step aside from your question and suggest you listen to my college @steve626 . Usually only respond to the Original persons question