Please check the following

・Have you enter 6-digit number? (Do not include space among numbers)
・Have you enter last number? (The numbers will become unavailable after about 30 to 60 seconds.)
・Have you enter number for CAS? (Does authentication app show "NU Central_Authentication_Service" over the number?)

・Does your authentication app works on terminal with precise clock?
Please check the following page.
https://www.nict.go.jp/JST/JST5.html
If it is not correct, please set the time to "automatically adjust" from the terminal settings

If you cannot access with the above, please try the following
・Login again after accessing https://auth-mfa.nagoya-u.ac.jp/cas/logout
・ Restart the browser and log in again
・ Restart the terminal on which the browser is open and log in again.

If these do not resolve the issue, the cause is one of the items listed below

・Did you fail to register your Authentication Seed?
(The cause may be that the procedure for registering the authentication seed to multiple apps is incorrect, or that you forgot to press the registration button on the QR code screen.)

In case of fail to register or invalidation of past settings
Access the authentication seed management page ( https://auth-mfa.nagoya-u.ac.jp/gauth-manager/ ) again.
Please redo the procedure of generating / registering the authentication seed and setting it in the authentication application.

The authentication seed management page can only be accessed from the campus network.

If you cannot come to the campus
Please apply as shown on the following page
https://icts.nagoya-u.ac.jp/en/services/nuid/CAS/#