Denied flight because i did not have online COVID 19 declaration for Kenya

I booked a flight with Ethiopian Airways from Joberg-addis- mombasa return. I arrived at the check in at 0900pm..flight was leaving atc1130pm...because of many people..i was 3 from last. On reaching the counter..i was asked if I have a QR code for Kenya on Covid 19....when i said No...they refused to check me in. I did the QR code but kenyan systen was down..it was showing success but dies not send the code.Last trip to Kenya with the same...i did the QR code while in Kenya..its unfair for to be denied flight because of a QR code which the i was told its the managers decision. Its unacceptable by ET....