Rex refusing to go unconscious from crossbow tranq arrows

I was just on ASE, Singleplayer on the island and tried taming a level 112 Rex with my 129.2% damage ramshackle crossbow. I looked at dodorex to see how many tranqs it would take, then decided to bring about 40 more than needed just in case, I shot every tranq arrow into it and it didn't go unconscious, Does anyone know why this happened and what i can do about it?