The debug notice is telling you there’s a non-static method called get_by_parent() which belongs to class BP_Groups_Hierarchy. Somewhere in your site, the method is being called statically like this BP_Groups_Hierarchy::get_by_parent(). You can’t do that in PHP as only static methods can be called in this way.

Looking at the debug…[Read more]

The debug notice is telling you there’s a non-static method called get_by_parent() which belongs to class BP_Groups_Hierarchy. Somewhere in your site, the method is being called statically like this BP_Groups_Hierarchy::get_by_parent(). You can’t do that in PHP as only static methods can be called in this way.

There’s likely a plugin, theme or custom code snippet you have installed still using the deprecated function bp_core_delete_notifications_by_type(). The notice is telling you to use bp_notifications_delete_notifications_by_type() instead.