Thank you for reaching out to us. Email which you receive stating Azure Active Directory did not register a synchronization attempt from the identity synchronization tool in the last 24 hours is related to Identity synchronization which has stopped for your tenant [PEBL779.onmicrosoft.com].
To resolve this issue, access your Azure AD Connect server, find the error why Azure AD synchronization has stopped working.
Refer to this article to troubleshoot this issue https://learn.microsoft.com/en-us/troubleshoot/azure/active-directory/directory-sync-stop-register
If the issue, still persists let me know, we can connect offline and troubleshoot the same.
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