If the option to disconnect the user is greyed out, here are some troubleshooting steps you can try:
- As suggested in this technet post, open an administrator command line and run “net user”. Then use the account here, “machine name\account name” and ensure that the account can be used to login the machine.
2)If you are having issues unjoining from the original account, you can create a new local admin and login with that account.
- Right click on start menu and select Computer Management
- Select Local Users and Groups
- Select Users
- Right click in the pane and select add new
- Give the new user a name and password
- Click Create button
Then disconnect from your organizational account, restart, and sign in to the newly created local account.
If these suggestions do not work, please try these additional steps:
- Check if the Azure AD Connect Server is in staging mode. If yes, remove the server from staging mode.
- If you know the Object ID of the device, you can use PowerShell to remove it. Remove-AzureADDevice -ObjectId “device-object-id”.
- There is a bug in some versions of Windows that prevents computers from being unjoined if the computer's name was changed after joining to Azure AD. If this happened, you would need to change the computer name back to the original name in order to unjoin it. You may be able to locate the original computer name under the registry key: HKLM\Software\Microsoft\SchedulingAgent\OldName
If none of these suggestions work and you still face this issue, feel free to email me at AzCommunity@microsoft.com ("Attn: Marilee Turscak") and include your subscription ID and link to this thread, and I will open a one-time free support case for you to get this resolved.
If the information helped you, please Accept the answer. This will help us as well as others in the community who may be researching similar issues.