When I un-check the party plug in the summon worked immedatley. I am assuming it is because of the party limit parameter but I am not 100% sure
You can try playing with the "exceed party limit?" option in Plugin Manager -> MK_Summon. However, I no longer work on this feature as RPG Maker's core code doesn't support it well.
I seemed to have gotten it working. I exceeded max party and that seems to have fixed it
