here is the screenshot, taken at 5pm on Jan 17, so I should be able to register attendance for the first session
Looks like you might be running into this bug:
https://github.com/danmarsden/moodle-mod_attendance/issues/340
It will only show sessions to the user when their enrolment was added before the start time of the session. What should be happening is it should allow them to submit attendance if their enrolment was added prior to the session close. (rather than the session start)
It's relatively high on my priority list to take a look at but pull requests or funding is always welcome.
It might be that this was my problem. It has resolved itself, during the next class session everyone was able to register.
Is there a suggestion on how to avoid this issue? Such as create the attendance activity before anyone registers for the course? Or is it after? Ideally of course this issue should be fixed. At least there should be some discussion of it on the moodle page explaining the attendance activity, I spent a lot of time on this issue because I thought I was doing something wrong.
Wolfgang