As noted, Luke Harper suffered a knee injury in March and has been out of action since then. WWE never released an injury update on Harper but it’s rumored that he tore his ACL.
Harper confirmed on Twitter that he is currently out of action with a “lower body injury.”
— . (@LukeHarperWWE) May 16, 2016
If Harper is actually out with an ACL injury then he will be kept out of action for a few more months.