How to Resolve Azure AD Connect Sync Error DeletingCloudOnlyObjectNotAllowed

Scenario:

When you have Azure AD Connect (Hybrid AD) and removed/unsynced the user account from on-premises Active Directory.

After the next sync cycle, the synced user object in O365 (Cloud) appeared as an orphaned object deleted users section and you restored it.

In this situation, you will be receiving a synchronization error as mentioned below in the screenshot:

Resolution:

The user account object created in the on-premises Active Directory has an Immutable ID and you will need to nullify this ID so the Azure AD Connect understands to not find the deleted user's object Immutable ID.

To do this, follow the below steps:

• Open PowerShell as Administrator and run the below cmdlet:

Connect-MsolService

• Enter your global admin credentials.
• Run the below cmdlet below:

Set-MsolUser -ObjectId '<user's object ID>' -ImmutableId "$null"

• Trigger a delta sync by running the cmdlet below:

Start-ADSyncSyncCycle -PolicyType Delta

Note: Before making any changes, make sure you are performing the steps to user object in question