If you or your students are having difficulty joining your Meet, you should try resetting your Meet link.
1. Go to classroom.google.com
2. Click on the class you'd like to reset.
3. Click on the Gear menu in the top right to get to the Settings menu
4. Scroll down to Meet.
5. Click on the down error and choose reset.
The old link for your class will be disabled, and the new link will become active immediately.