I'm facing issue accessing kentico admin after a successful upgrade from Kentico 12 MVC to Kentico 13 MVC.
The admin page coming fine and then will trying to login to admin if throw this error message.
No clue what I'm missing here.
Have you checked the event logs in Kentico via SQL? How about the server event logs? Those two areas will provide you with more information than anyone here can give.
Also try clearing your browser cache. Recently had the same error with a fresh installation of the Dancing Goat Core sample site. Clearing the browser cache and restarting both applications fixed it for me.
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