After refreshing the page, are the posts merged? If not, then I can only assume that you have incorrectly configured the system of user group rights. You can try to set such settings for checking.
Plugin versions before 3.0.0 support Xenforo 2.2.x. But I recommend upgrading to the latest stable version of Xenforo, because a lot of work has been done in the latest versions of the plugin to optimize the use of server resources.
Added setting to allow filtering for a custom field
Fixed a bug where having radio buttons in filters with the “Required” option enabled prevented filtering.