Thank you for posting this in Microsoft Q&A.
Do you mean you have deleted all the device for a user in Entra portal. Now you are trying to add another device for same user in Entra portal and you are unable to see that device.
If this is the case then post removing the device from Entra portal for a user you can perform below steps to leave the device from Azure AD,
If the device is Azure AD joined then ensure creating a local admin account on the device followed by:
- Open the command prompt as an administrator.
- Enter dsregcmd.exe /debug /leave.
- Sign out and sign in with local user you just created.
If the device is Hybrid AD joined then follow:
- Open the command prompt as an administrator.
- Enter dsregcmd.exe /debug /leave.
- Sign out and sign in with on-prem account.
Post this you can try to remove the device from Azure AD.
Once done you can rejoin the device to Azure AD.
Let me know if you have any further questions.
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