I would suspect this is related to the recent change UIS enabled on the 14th Feb. that changed the way we all login to RAVEN, which has now been replaced by the Microsoft login screen and also requires users to have enabled MFA authentication.
Information about this can be found here https://help.uis.cam.ac.uk/news/raven-login-change
You may get 'Stale request error' messages and fails with MFA. The solution to both of these is often to keep trying the link or bookmark and keep going through the MFA login process and you will get through.
If that fails then go into your browser's privacy settings and delete all stored cookies and cache data (to be on the safe side I would do it for all time) close and reopen your browser and try again. The entire login process (old and new) uses a vast number of cookies in order to make it work - if corrupted they will cause access to fail and, until removed, always fail. I suspect the issues people are having are connected to the clash between old and newly stored cookies which are causing false error messages - such as 'stale request'.
There is a screencast here https://sms.cam.ac.uk/media/2203114 that helps to explain further how to do this.
You can also try a different browser, to the one you would normally use, to see if that makes a difference.
If you are still having issues, having tried all of the above then you will need to contact UIS service desk servicedesk@uis.cam.ac.uk and you should explain you have spoken with the library and have been referred to them.
Finally, I should also point out that this not actually required to login to iDiscover when accessing eresources. Simply use the search facility in iDiscover (without logging in at all) and then enter your RAVEN credentials when prompted to do so by the resource you are trying to access.
I hope this is helpful please get in touch with the lib-raven helpdesk raven@lib.cam.ac.uk if you need further help or advice.