User has lost access to his license

The following article lists some troubleshooting steps: https://helpx.adobe.com/enterprise/kb/resolve-trial-and-license-expired-errors.html

I'd start with asking the user to sign out and sign back in. If after entering their email address, in case they're prompted to choose an account, ask them to choose the business account and not the personal one. On the Admin Console, can you verify that the user has an assigned a license. The user can also verify if they have a license by signing in to accounts.adobe.com. If the product license isn't present, then you can try assigning them a license again from the Admin Console. Remove the product from the user. Save. Wait for a few minutes (user may get an email that they no longer have access). Then add the product again.

If you've established that the server end is okay, then there might be something going on locally on the users machine. You can look for probably causes in the document listed above. Again, as this is recent, do look/ask for recent actions performed on the computer. Any new software installs. Firewall updates, anti-virus etc that may cause some changes.

Let us know what you find.