I'm working through the COVID-19 exam credit extension process right now for Washington State. I could not find any guidelines online about what to submit either, so I reached out to my state board to ask what kind of documentation they needed. I got bounced between the state board and NASBA three times, each of them saying that the other responsible for evaluating credit extensions.
Eventually, I did get ahold of someone at NASBA who was super helpful. He said that the extensions are granted on a state-by-state basis, and that they need documentation for basically everything.
For example, I not only had to prove that my roommate had a positive COVID-19 test, but I also had to provide our matching rent invoices to prove that I lived with him. I don't know if mine will get granted, but I think the best bet is to provide the maximum possible amount of evidence. If you make a claim, have documentation to support it.
The NASBA employee said that he's thrown out credit requests who just provide proof that they had COVID or something like that without proof that having COVID disrupted their exam experience. You might need to provide medical documentation that shows you are immunocompromised. He also said that credit extension requests got denied if you were testing during the period of time that you claimed you couldn't test, even if the testing seriously endangered you. I am concerned that might happen to you if you applied for an NTS at any time between the start of COVID and this spike. Maybe it would help to have a note from your doctor saying that testing now, during a COVID spike, would seriously endanger your health? It sounds like they're being stringent with granting exam credit extensions.
Another thing to keep in mind is that when I talked to him last Friday (1/15), he said that they were still processing requests from late November/early December, so it's unlikely to hear back on any requests for at least 4 weeks. I'm glad they're still processing them, but it might be quite some time before any of us hear back.
I hope this is helpful, and I'd love to open up more conversation on this topic as I'm sure many people are wondering how to get COVID-19 credit extensions. Since the state boards and NASBA aren't providing any clarity or guidance, I think we can all come together to help each other. Best of luck!