It's a game thing. When I first started using MQ2 I was having similar problems. When I was unable to use KA to assist my pet I'd unload MQ2 and do a /target petname and wouldn't target the pet. The issue is totally random however. If I was killing in a zone for a little bit and then would try to target again, it would work. Then if I tried it with MQ2 it would be fine.