Pre assigned Break Out Rooms

[jilanneholder]

We are running an event with pre assigned break out rooms. Most people managed to get pre assigned and we only had a manually add a few.  We did have a couple of people who came late and couldn't sign in. Would this be because they weren't on the spreadsheet? If I upload a spreadsheet to pre assign break out rooms does that mean anyone not on the list can't join the meeting?

We are running 3 recurring meetings, will I have to upload the spreadsheet again if we want to include the extra people for the next meeting? 

[jilanneholder]

Also, we have a few people who are showing on the participants list but when I go to move them to a break out room, they aren't showing on the break out rooms panel. What can we do to move those people across? Or do they have to leave the meeting and come back in?