Hi Carrie,
I'm here to help,
If you’re unable to add users to a shared calendar, it’s likely because you don’t have the correct permission level. Only the calendar owner or someone with Full Access or Editor permissions can manage sharing settings. To check or change this if you have the right permission please try go to Outlook Calendar > Right-click the shared calendar > Properties (or Sharing Permissions). Under the Permissions tab, you can add users and assign permission levels like “Can view all details” or “Can edit.”If the option is greyed out, you’ll need to contact the calendar owner or your IT admin to grant you the necessary access first.
Warm Regards,
Cherrelyn