You could use the troubleshooter:
Consider unchecking that option, saving then re-checking it.
If all else fails, I would remove and resinstall the AADConnect Server installation if you can.
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I have a strange issue with the hash password sync.
before all worked fine, but after aour connector crashed and all domains were unmarked to sync, and then again marked to be synced with AAD two subdomains, are not working fine, all users' password from these subdomains are not synced with AAD. the troubleshoot tool of Azure connector showes all is fine, no errors.. however when an user changes its password, its stay only in AD.. is there is any other way to check what is happening here?
You could use the troubleshooter:
Consider unchecking that option, saving then re-checking it.
If all else fails, I would remove and resinstall the AADConnect Server installation if you can.