Debug activity access problem - https://buddypress.org/support/topic/post-update-unable-to-see-the-buddypress-activity/

activity-access.patch

Index: src/bp-activity/bp-activity-screens.php
===================================================================
--- src/bp-activity/bp-activity-screens.php
+++ src/bp-activity/bp-activity-screens.php
@@ -250,6 +250,8 @@
 	}
 
 	// If activity author does not match displayed user, block access.
+	var_dump( bp_displayed_user_id() );
+	var_dump( $activity->user_id ); die();
 	if ( true === $has_access && bp_displayed_user_id() !== $activity->user_id ) {
 		$has_access = false;
 	}