Try to take a deep breath. Check online EVERY HOUR or two for available test dates. There are test takers who cancel and dates become available within a blink of an eye. The entire month of July was closed in my city, three adjacent cities, and the closet state. I continuously check for three days, 2 am, 5 am, 8 am, 11:30 am, 3:15 pm, 10:30 pm, etc. You get the point. At least three dates with various times became available in July.
I dare not tell you you should have planned better, its not Pearson Vue's fault, blah, blah, blah. How therapeutic would I be as a near future RN to someone who is panicking.
Unfortunately, you were not completely aware of the policy regarding the ATT expiration date. Its ok. WE ALL make small mistakes or misinterpret language, directions, policies, etc. Just diligently keep reviewing Pearson Vue website. You may just find an available date where someone canceled. Best wishes!