According to your information above, it may caused by some rules created in Outlook for Mac are not saved on the Exchange server.
You could try using below command to check whether the rule is saved successfully
Get-InboxRule -Mailbox Joe@Contoso.com | fl
In addition, as the reply above, try using OWA to check the rule, remove and re-create it again to verify the result.
The official KB here introduces about The rule I created does not work for your reference as well