Just because a phone rep was able to get the order to go through doesn't mean your account is fine. If you're paying with a CC/Bank Card and you know your entered the billing information correctly and orders won't go through or IMMEDIATELY get cancelled your account has been flagged and is no longer good.
If you're trying to check out with a Gift Card the error could be with there site as they've had problems processing gift cards for quite some time now. Sometimes it works sometimes it doesn't.
However I do know that if they limit something to 1, 3, etc. and you use the same account to place multiple orders back to back to back to back, etc. then there is a good chance your account will be banned.
The other guarantee is that if you try to mess with their bundle policy (i.e. buy something that comes bundled with something else and send the free item to one store, pick it up, send the paid item to another and try to cancel it or let it time out so you get one item free or reduced [depending on the terms of the bundle]) they will ban for that as well.