Cannot Buy Fliegerfaust From Armoury

Hi I can't buy the fliegerfaust from the armoury. I am able to buy other weapons, so this problem seems specific to the fliegerfaust (at least for me, and for now). For example, I was able to buy the bazooka a few days ago, and I bought a scout carbine pistol after being unable to buy the fliegerfaust, just to be sure. I have the company coin available and I am able to press the unlock button but once it's done "processing", nothing happens; no company coin is spent and I do not unlock the fliegerfaust. I have done some searching and people seem to be suggesting that I remove the grenade/gadget slots and changing to vehicle buster but the problem persists.

Any help would be appreciated.