Initially tried Chrome with the CORS extension, went right to the "header non-thai" error. Used Chrome Incognito and got the success notification on the first attempt, no errors. Used a gmail address and received confirmation email immediately after. I had the J&J shot, no issues submitting 1 dose and it did not ask for a second. I did add my passport number to my U.S. CDC card. No spaces added to passport number or anywhere else in the application. Fingers crossed, flying on the 10th.