Thank you for asking this question on the **Microsoft Q&A Platform. **
In your Azure AD go to this URL https://aad.portal.azure.com/#blade/Microsoft_Azure_ADHybridHealth/AadHealthMenuBlade/SyncErros You should see something like this
Also, you can look for more details on your azure AD connect server, look for the following tool
you will see a screen like this one
Where you can see detailed information on the errors.
Hope this helps,
Carlos Solís Salazar
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