Make sure you paid your BON fee-if the state has one, and then the 200 testing fee, once you paid BOTH, then you get your ATT by email. If you haven't paid for BOTH, you will not receive your ATT...
Usually your school makes you fill out the paperwork, then it us up to the student to foot the bill, UNLESS the fees are included in the tuition. I paid for my licensing fee, then paid for my ATT once I confirmed my paperwork was accepted at my state's BON. I then paid for the test, and got my ATT less than 24 hours.
When I was in my PN program, we filled out the papers and paid by money order and our paperwork was sent to the BON by the time we graduated. Within 2-3 weeks, the ATT was received by mail.
To the OP, this seems abnormal ONLY if you paid and received nothing. I would backtrack to your school to find out when they sent your paperwork. Once you find out when, then contact your BON to confirm that you paid and paperwork is in their system. If that checks out, then contact the testing center if you paid to find out when you should get one, and it's been 3 months. They should look into it and you should get it as quick as under 24 hours or a long as a month.