Pre-assign Breakout Rooms

Welcome to the Zoom Community, @Rob313.

By pre-assign, I'm not sure if you mean assigning within the meeting, or before the meeting with the CSV upload.  It shouldn't matter... but assigning people during the meeting will work for everyone, unless they leave the meeting prior to starting the Breakout Rooms.

For CSV uploaded pre-assignments, it "does the best it can with the information available".  If there are matches between email addresses imported and email addresses of users logged in with Zoom accounts, they'll work fine.  Any user that is not logged into Zoom and/or their email address doesn't match one in the uploaded data, they will have to be assigned (or can self-assign, if that permission is enabled).