[Plugin: BuddyPress] Some pages work and some no

Hi,
I’ve got a strange problem. I’ve installed BuddyPress and wanted to run in on my page homosekusalizm.org.pl – I did all I was supposed to do.
my links are https://www.homoseksualizm.org.pl/index.php/whatever, so I did all I was meant to do with this stuff (https://buddypress.org/community/groups/installing-buddypress/forum/topic/404-error-on-bp-links/)
but the problem somehow remains. for example if I go to https://www.homoseksualizm.org.pl/index.php/members/admin/ it works and I see the page, but for ex. https://www.homoseksualizm.org.pl/index.php/members/admin/activity/ brings me back to my home page – although the link is as above

any idea what to do?