Users not syncing between AD and Azure?

Question

Active Directory

Good afternoon, synchronization between the cloud and the local area flies without errors, but new users have stopped appearing in the cloud. I did not make any changes, tell me where to dig?
Users do not fly in both directions. IDFIX throws big userPrincipalName errors

Answer 1

It's hard to tell from your description, but errors about UPN could mean exactly that. Usually, new accounts are assigned a local suffix established under the king of peas, such as mycompany.local, when they connect to the openwork, they add a new suffix like mycompany.com.
Probably new users get the default UPN, and the old ones have been changed, but this is just a guess.

Answer 2

View sync conditions in Azure AD Connect.