United Airlines complaint: Refused to board

On Thursday 8th of October I had a flight from Halifax to Toronto with a connect flight to Houston (23 hours layover) and then to Belize. Check in was very slow and when it was my turn, I was asked for the Belizean health app. I replied that I will download it in Houston during my 23 hour waiting time. That was not accepted and because of the slow check in there was no time to download it. I had to rearrange my flights. Instead of 6 am I was able to leave Halifax at 6 pm. In the evening no one wanted to see the health app. Then I had to spend an additional night in Toronto and to postpone my stay in Houston for one day. So overall I was one day late (lost one work day one additional night at a hotel in Toronto re-booking fees for the flights). The extension of my travels due to this unreasonable request (which is not a requirement by any government) also caused a higher exposure to other people, especially in the Corona hot spot of Houston, Harris. I had a valid air ticket, a valid passport, an ESTA, proof that I’m allowed to enter Belize. It is nowhere written, that I had to have the Belizean Health App before entering the plane on the very first leg!