level 0 or 1 login gets 404 error

I have ben fighting to get the login to work. I managed to get a registration page and a log in page but can not log in as a user. When using the log in window I get a 404 error.

I have no pay-pal buttons in my registration form as people will get invoiced later, if they do it via the website (level 1). This is because we need to check their professional registration before we can accept them. Level 0 is free and restricted.

I also looked for instructions how to create log-in and log-out procedures but could not find anything that seem to relate to my problem.

My domain URL for logging in looks like this:

http://xyz.eu/membership-options-page/?_s2member_seekingtype=page&_s2member_seekingpage=511&_s2member_seeking_uri=L3Rlc3QtZm9yLWxvZ2luL3Bvc3RzLw%3D%3D&_s2member_reqtype=level&_s2member_reqlevel=0&_s2member_restype=page&s2member_seeking=page-511&s2member_level_req=0

Anybody got an idea?