For the online demo website
you need to use a temporarily username and password. Credentials for username admin are taken. You should use your username and password. Let's say username: user0012, password: 1wesd. Then, choose if you want to be logged as a power user or writer.
As for the TIU sample site, credentials are as follows:
If the above does not work, you can restore the password through the database.
Check out the following article: Resetting-administrator-password
I hope this helps.
the Telerik team
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