Hi @avitkiba ,
As I know, it is indeed impossible to get add-ins from a shared calendar in Outlook desktop client. And Microsoft provides two workarounds for this issue:
- 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.
For more information, please check this document: Office add-ins aren't available from a shared calendar.
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