Have given 3 people owner rights on resource mailbox meeting rooms. But new appointment is grey out then later inst. it happens to everyone that i gave owner rights to from another persons outlook

Please describe exactly and completely what you're doing, exactly what you see, and what you expect to see.

Hi,

Please run the following command to check your calendar permission and mailbox permission about this resource mailbox:

Get-MailboxFolderPermission -Identity Room1:\Calendar
Get-MailboxPermission -Identity Room1 |where {$_.AccessRights -eq "FullAccess" -and $_.IsInherited -eq $false} | fl

Please share the results here to confirm whether the permission is configured correctly or not. Additionally, please use Outlook Online mode or OWA to create new appointment with Owner permission to have a try.

Regards,