The /invitations
API is the endpoint used to invite external users to join your organization. It cannot be used to invite internal users to join a meeting.
If you want to send meeting invitations to internal users, you can try calling the /sendMail endpoint to send a custom email and attach the meeting URL to the email content. Alternatively, you can add attendees when you create a calendar event, which will automatically send an email to the invited users.
Hope this helps.
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