Office add-ins aren't available from a shared calendar

How to enable add-ins for a shared calendar 

Problem
When sending a meeting request from a shared calendar, the Office add-ins aren't enabled on the ribbon.

Solutions
To use Outlook add-ins while creating a meeting request for a shared calendar, you can use the following workarounds: 

• If you have full access to the shared mailbox and are not a delegate of it, add the shared mailbox as an additional account in Outlook. 

• Use Outlook on the web to open the shared mailbox calendar and create the meeting request with the Office add-in. 

Enabling add-ins when sending email from secondary email account

Problem
You intend to send a meeting request from your primary email account, but the Office add-ins are enabled on the ribbon. However, when you select a secondary email account, the Office add-ins are not enabled on the ribbon. 

Solution
​​​​​​​To work around this problem, use Outlook on the web to open the shared mailbox calendar and create the meeting request with the Office add-in. 

See also

Office add-ins are not available from Mac shared calendar