When I add a multiverse command with to my npc it teleports me there but says unknown command

Use the command '/npc cmdinfo' There might be another command running that you added that you forgot about that isn't valid.

I checked and it only said the 1 command I used "/mvtp a:tntrun"

If you have the '/' in the command remove it. Don't know why it would say Unknown command, if you don't have the '/' in the command. Yet it still teleported you there.