E-11d problem can’t equip after unlocking

I got the achievement that I unlocked the e-11d and when I go to use it in a battle it’s not there, so I went to the achievements where I read before I needed 50 kills on co op to unlock it but it wasn’t there anymore. 

-note that when I unlocked it I left the co op match cause it wasn’t i couldn’t equip the gun and it wouldn’t show up In my guns