[2020] Mantis bug (no pun intended lol) where it won't let me reroll it

I for some reason I can't reroll my mantis even though I already have the weapon itself and the blueprint. It'll prompt text on my screen saying "you don't have the requirements" or something like that. All my other exotics are able to be rerolled except for my mantis. Can someone give me an explanation as to why this is happening because I'm honestly confused......