The issue has been resolved.

A fix has been implemented and verified in the production environment. All affected users should now be able to log in to their hybrid EBA/MSP accounts. The incident is currently in state of being monitored.

We have received multiple reports from customers who are unable to log in to their hybrid EBA/MSP accounts. The issue appears to be global, but affects only a very small percentage of users. Our development team is working on a fix.