Single registration for all occurrences of a webinar

We have a webinar set up with multiple occurrences on three days one week and then three days the next week. Each day has multiple sessions, although not consecutive. It's set up with registration and attendees registering once  can attend any of the occurrences. Upon registration, an email is sent with the Zoom webinar link info so that the person should just be able to click the link and get to the webinar. We have experienced the following issues and wonder if anyone else has also and might have a solution:

1. Some people have been successful at logging in and getting into the first session of the first day of the webinar, but after that are unable to get in. It can be the next session on that same day or the next day. Or sometimes it worked the first day, not the second, but then worked again on a day during the second week. It seems haphazard as to why they can get in sometimes and not others. And then there are some people who have no problems and can get into all of the sessions with a single click on the link in their registration email. Why would someone be able to get into part of the webinar and not the rest when the registration is set up for being able to attend any occurrences? We have temporarily solved this by either entering that person as an invited guest and then changing their status from panelist to attendee or re-sending the Webinar invitation email and having them try to click the link again. Neither of these are ideal. We would prefer a solution so that our webinar attendees do not have any login or access problems.
2. Some people are asked for their Zoom account password when they click on the webinar link in their registration email while other people just click on the link and it connects directly into Zoom and the webinar. Why would there be this difference? Does it have to do with the settings on their computer or how they configured their Zoom account? Is there a way to walk someone through to change this so they are not prompted for their Zoom account password when entering our webinar?