Cannot reach wp-admin

Greetings,

Yesterday I have updated a theme, but after that I could reach wp-admin normal way, I got redirected to this:

http://www.mysite.com/wp-login.php?redirect_to=http%3A%2F%2Fwww.mysite.com%2Fwp-admin%2F&reauth=1

I tried to recover a back-up of 1 day ago and the same problem showed up.

I tried a clean install without any themes or plugin other that the default ones that come with the installation of WordPress. Same problem.

Removed cache from my computer, tried 2 browsers and have tried to login on different computer. Same problem.

Help please, thanks in advance.