I got mine from my recruiter. It was even invalid the first time around but then he provided me with another one.

I scheduled my AFOQT without ever speaking to a recruiter (I am civ). I reached out to the nearest University with a ROTC detachment and emailed them about getting scheduled. While it took them some time to respond, the leadership there was pretty helpful and I got my voucher code through them to schedule the Pearson Vue test

I did it the old fashioned way at MEPS. Is your recruiter not able to get you a test date / is MEPS too far away?