1. Does the issue occur to all your federated users, no matter they’re trying to access from external computers or internal ones?
It happens for all users and both internal and external computers also.
2. Does the issue occur to IE only? How about other browsers?
Other browsers too.
3. Does the issue occur when trying to access OWA only? Please let an administrator (who is on a federated domain) try to access the Office 365 admin portal to see if the same error occurs.
Yes OWA only.
4. When did you complete the ADFS configuration for your Office 365 organization? Did the issue occur back then?
It was completed 1 or 2 years before I join this organisation.
5. As you mentioned “frequently”, does it mean the access can work sometimes? In other words, the issue cannot be reproduced every time?
Frequently means the error we receive is frequent and every time we need to refresh the browser or reopen the browser then we will be able to login successfully. All the while we advise user to do like this.