Ugg.com / Deckers Outdoor – Not able to use store credits

I have been trying to use my UGG store credits to place online orders for the last few weeks( since the end of September).
I have a few credits for over $500.00 in total. The UGG.com website is accepting and confirming my orders. Also, the website correctly displays the available credit amounts, but unfortunately all my orders are getting cancelled in an hour or so for the strange reason : "Unfortunately, we're unable to fulfill it due to problems with the payment or billing information provided. "
I am using store credit - so no additional billing info is needed.
I have contacted UGG customer service plenty of times, but no support was provided to resolve this issue. The only resolution they offer is to try again in 24/48 hours or use the credit card. The only explanation provided by customer support is that it's probably a glitch in a system and it happens sometimes. Does not sound professional to me.
I have been trying for a few weeks already and cannot get any help in using store credits.