Overview
The ability to send meeting invites in the Zoom application requires logging into the Outlook application with two-factor authentication (2FA). The web version of Outlook may show calendar updates when sending a Zoom invitation, but the actual invite will not be sent/received without signing into the installed Outlook client.
Solution
Before sending a Zoom invitation, open the installed Outlook application (non-web version) and sign in with 2FA.
Note: More information on 2FA can be found HERE.
Symptoms
Old Zoom meeting invites send all at once
New Zoom invites aren't sent/received