Jack

Well the problem was actually with your plugin in my case( mine was slightly different from @mariyahu as I could not have any user logging into the wp dashboard. even the administrator).

I deleted the plugin, went into tables in my db using phpmyadmin removing settings. That worked eventually

Hey, did you finaly figure out what the issue was, I tried @ramley trick but didnt work for me. Login works but i just wont be redirected to the backend. even after installing this plugin