… the activation link sent to users who want to register to my account doesnt activate the account and I have to do it manually

Can you please post the URL of the activation link from the e-mail? We had a thread with a similar issue two years ago, where the URL of the forum address in the settings needed only a trailing slash.

 
// from
$settings['forum_address'] = "http://www.example.com/forum";
// to
$settings['forum_address'] = "http://www.example.com/forum/";
 

Attention: This is only exemplary code. Change the setting in the admin area, if this is the issue!

Tschö, Auge

[edit]A further case of absence of the trailing slash that leads to the same error (german language).[/edit]