I've also faced this the 2 times I tried to buy a flight on the EK website. Credit card always gets declined even though I've called the credit card company to clear it. Apparently per the call center, the EK website also has a 3 strike limit to credit cards getting declined and only gets reset after 24 hours.

EK seriously do something about this. If I end up calling the call center, please take my $$$. I ended up booking on Expedia and if there were other airlines, I would NOT hesitate to book with them instead of EK.