have no Nanosuit Reboot option, but I am 50.
Module 22/23..

First of all, why you'd want to prestige is beyond me, but it's your choice so whatever.
You don't get the reboot option AT level 50, you get it AFTER completing the exp requirement for an "imaginary level 51."
Basically means you're not at max rank until you've gotten to level 50 and then like 70k more exp or something... Don't remember how much exactly, but 50k-80k exp I think...