BuddyPress.org

hi @nnc24,

you have to read and to debug. As first test, activate 2015 theme and deactivate any plugin but BP. Put debug mode on true in wp-config during your test.

Some related topics:
https://buddypress.org/support/topic/user-activation-issue/
https://buddypress.org/support/topic/new-user-registration-problem-invalid-activation-key/