You are using the entra-connect (ex azure-ad-connect) to sync user properties/passwords?
Do you use on-premises-ad installed version or cloud versions?
Do you use password hash sync (phs) or passthrough authentication (pta)?
Please provide more information about you sync architecture and its status.
Most likely you are using on-premises ad installed entra-connect and in that case see the synchronization log in on-premisess synchronization service - are there errors.
Also check the 365/Entra sync status for errors and post them back.
https://admin.microsoft.com/Adminportal#/dirsyncmanagement
https://aad.portal.azure.com/#view/Microsoft_AAD_IAM/DirectoriesADConnectBlade
Do you still use v1 that stopped working on October 1, 2023. In that case you should upgrade to v2.1.16.0 or later, preferably latest.
Regards