Thank you for posting your issue in our forums.
Let me first elaborate on the problem you have.
It might be caused, if the applicationPool is not set ClassicMode.
Please try running
the application under ClassicMode application pool. If the problem persists,
you could try resetting the administrator password through the database.
"The hashed format
of a password is stored in the database table Telerik_Users. In order to access the
password, the password format should be changed - the PasswordFormat value should be set from 1 to 0 (put into "Clear" mode) so
that the password is saved as plain text in the table. After executing
this, the new format of the password will be saved in the Password field. Copy this string and paste it
into the password field when logging in into the Admin part of Sitefinity"
Now about the details,
I believe that they are important for everyone. You might not believe it, but they are important for us as well. That is why, we will appreciate if you could elaborate on the problems you have, the difficulties you have met, and share your oppinion/experience. You can mail me directly on firstname.lastname@example.org if you wish. I assure you that our team is ready to assist you with everything related with Sitefinity.
the Telerik team
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