Why is my money no good with MoneyGram?

So I’m trying to send $200 from the USA to Argentina. The person in question prefers MoneyGram. Problem is, eMoneyGram.com has been canceling my online transfer requests and acting very cagey about it – I get form emails saying “call our 800 line” or “do it in person”. They already have my checking number, backup credit card, phone and various other pieces of ID – is anything good enough for these people?