Cannot login or register using UM forms

After activating UM on my site, i cannot login through the UM login page but i can login through the default wordpress login page (wp-login). The UM login page just reloads the same login form after I enter my username and password, same as the register page, new users cannot register unless the default wordpress register page is used.

Any suggestions? i am willing to give out my wordpress login details for you guys to take a look.