If Google Meet suddenly does not work on Chromebook:
Refresh the device: (Yes, I posted this for a different problem, but it works for this problem, too!)
https://sites.google.com/newbedfordschools.org/kms-resources/chromebook-wont-turn-on
Then update the device:
https://sites.google.com/newbedfordschools.org/kms-resources/update-chrome-all-school-devices
Then shut down the device and restart - it should now work.
If it does not work, clear the cache, close and reopen the browser and try again: https://sites.google.com/newbedfordschools.org/kms-resources/clear-the-cache-in-chrome
Chromebooks should be completely powered off and restarted at least once a week to stay updated.