Do you see the hidden rule via powershell for that malbox?
Get-InboxRule -Mailbox Joe@Company portal .com -IncludeHidden
https://learn.microsoft.com/en-us/powershell/module/exchange/get-inboxrule?view=exchange-ps
You can also Check with MFCMAPI for that user:
https://o365info.com/delete-corrupted-hidden-exchange-inbox-rules-using-mfcmapi/
Another option is to back up the Outlook rules then run:
Outlook.exe /cleanrules
and then re-add the needed rules via Outlook