Can't login in admin

[kenni]

Guys, this problem often occurs when you're using plugins, and as far as I know, this solution should work on 95% of all the issues people have with logging in and being redirected back to the login form.

Check your installed plugin files. It seems theres a problem, when plugins have empty lines and spaces in the end of the plugins .php files.

Go to the very end of these files, check for extra spaces/lines immediately AFTER the very last endPHP tag ?>

Of all the times I had this problem, this solution worked for me every time.