@jennyKim Thank you for reaching out to us, whats the date of alert this was reported? Last week (on 6th March) this was reported by few customers where our engineering team investigated the issue and mitigated the same on 9th March.
If this alert is persistent, would request you to check this doc - https://learn.microsoft.com/en-us/entra/identity/hybrid/connect/tshoot-connect-password-hash-synchronization related to password hash sync which will help to check the health of password sync to your tenant.
If the issue still persists, lets connect offline and we can investigate this further (sharing my contact details via private message).
Please remember to "Accept Answer" if answer helped, so that others in the community facing similar issues can easily find the solution.