Some have used the Teams Check-in, Some join directly from the Calendar.
Nearly all of those attended registered. Some joined who didnt register. Others attended from the Teams Check-in button on the email or directly from their Calendar. "Join meeting now".
When connecting they either join via Web app or Teams Client. Those that join via web app are not showing as checked-in.
Some registered in 365, appeared on the Teamd attendance report with the same email as when they registered, but didnt show up on the Check-ins on 365.
Its all a complete mess. Basically measn that the "If Attended" liked to event is used on a CJ. This will no longer work as it did with Teams Live Events.
Something that your 365M developers and Teams developers have not throught through properly.
Likely Outcome
This means i will need to change my Webinar CJ templates and remove the Post event "If attended" and instead use "If registered" This means new email templates will need to be created.
If attended looks like its not completely redundant as only a handful of actual attendees are showing as "Checked-in"