Members not able to join channel meetings

Hi all 😃

I am using Teams to deliver training events where many of the attendees are joining as external guests via an emailed link.

They are able to join the general meeting no problem. When I create a channel & then enter it and use the participants panel to try & invite members into the channel, some of them briefly look like they are being invited but then do not receive the option to join the channel meeting??

Is this a common glitch or have I got something wrong in my meeting / channel settings??

All help / advice most gratefully recieved 🤞
Many Thanks
Clair