Ever since updating to iPadOS 15, we have been randomly getting teachers that get the error message "Configuration Not Valid - Classroom must be configured with a valid education configuration profile. Contact your network administrator for assistance." when they open the Classroom app on iPads. Jamf informed me it's due to PI-010204. The only fix seems to be to pull down a fresh copy of the EDU profile, either by assigning the iPad to a different user and back or assigning the user to a different class and back.
You can find devices that are having the issue by creating an Advanced Search for iPads that have the EDU profile installed but do not have "member: JSS Built-In Signing Certificate" installed.
I wrote a blog post with more detail here: https://gingerscripting.com/apple-classroom-configuration-not-valid/
Yep, we are seeing this quite a lot. I usually change one of their classes to refresh the edu profile. I'll take a look at creating an advanced search to see who else this is affecting.
Edit: wow, we have 185 iPads. Hope this gets fixed soon! I don't think changing the username of the device to someone else is a good fix for us as we scope apps and config profiles. If we assign it incorrectly they could lose work. Is there anything Jamf support can do to force a refresh of the edu profile?