Resolve identity provider OIDC or SCIM user account sync conflicts in Apple Business Essentials
If you disconnect from your identity provider (IdP) and reconnect, you can choose whether to merge the IdP accounts. After you reconnect, check the IdP provisioning logs. After all the accounts are synced to Apple Business Essentials, if your IdP supports it, you can choose to disable Auto Merge to avoid any account merge issues.
Manually resolve IdP user account sync conflicts
If you have a conflicting user account with your IdP, you can manually resolve the conflict.
In Apple Business Essentials, sign in with a user that has the role of Administrator or People Manager.
Select your name at the bottom of the sidebar, select Preferences
, then select Managed Apple Accounts 
.Select Edit next to the IdP custom sync section, carefully read the Account Conflict message, then select Resolve.
Select the Download Conflicts button to download a list of account conflicts, then review the conflicts.
If the conflicting accounts are identical to each other the IdP and Apple Business Essentials, select Merge.