Copilot Missing from M365 Portal

From one day to the next, Copilot Chat disappeared from the portal on one of our small clients' accounts.
It's available and working in all other Copilot applications, but it simply disappeared from the Office portal.
This is a premium business subscription without a Copilot license. The user has two PCs, and the problem occurs identically on both. No changes have been made.
Community, do you have any ideas or suggestions on what the problem might be?
Thanks