American Express Card Blocked for no reason

I received an American Express Corporate Credit Card a few weeks ago already. I haven't been able to use it once as the card has been blocked. Firstly, I tried paying for a coffee at ORT Airport and was told that American Express was not allowed at any of the shops in the airport. I then tried using it 3 times on my trip to South Korea without any success. I phoned the call centre yesterday and spoke to a lady who said the card had been blocked but that she couldn't see why. She was going to check and get back to me. This never happened. I am starting to regret getting this card and don't see myself ever using it, except in extremely desperate situations. Their service in just getting the card was like pulling teeth and took months.