We didn't have any problems with uploading the pdf of the negative test, or with a quick turnaround on their examination and approval of it. I think mine took a couple of hours. You must have every step completed at least 4 hours prior to your flight departure. Maybe that's where someone ran into problems?Thanks for the earlier reply. I forgot to ask one other thing. Regarding Verifly, I'd read that a problem with the app was adding the negative Covid test result from Mexico - not sure if the issue was being able to add it to the trip or there being enough time for it to be validated before one's return flight. Did you have any issues?
Was going to give it a try (also read that next year, Verifly may be required) but would also have all paper copies or pics on phone.