Product: Credit card or prepaid card

My 2 Amex gift cards ( {$1000.00} and {$1500.00} ) have completely stopped working on a huge list of online retailers. They used to work perfectly, which is why theres only {$500.00} left on the {$1500.00} card - because my {$1000.00} purchase worked without hassle. The same is true for why theres only {$90.00} left on the {$1000.00} card. I bought things from XXXX and multiple other retailers since XXXX  without having any issues whatsoever. Unfortunately, that is no longer the case, and even though I have enough money left on the cards, and the cards dont expire until XXXX, all of my purchases on XXXX XXXX XXXX XXXX or XXXX were blocked for unexplained security reasons, with multiple customer service representatives claiming Amex automatically blocks all purchases from a huge list of the most popular retailers. This is contrary to the claim both on the website and the customer service number that these cards work anywhere Amex is accepted. That used to be the case, but at this point, its false advertising. 

In total, both cards have {$590.00} left. The {$1500.00} card has {$500.00} left, and the {$1000.00} card has {$90.00}. This is a huge amount of money to arbitrarily no longer be able to use, and its even more frustrating because I thought I was saving money by not spending it all at once, but in that time, the cards became unusable due to Amexs issues, despite the cards not expiring until XXXX. 

I spoke to a number of people at Amex gift cards customer service number. XXXX ( ID # XXXX ) said it was blocked for security reasons due to the XXXX marketplace sellers fraudulent activity but I was buying directly from XXXX, not a third-party seller. XXXX said I cant use the card on XXXX anymore, even though Id never had issues with using the card on XXXX before, and the only issue Im having is being unable to use my Amex gift card to order from XXXX. 

I then spoke to XXXX ( ID # XXXX ), who said she removed the block and to try again in 24 hours. I tried it again 24 hours later and it still didnt and doesnt work. 

Twice instead of transferring me to a manager the music just stopped for an hour with no response. 

I spoke to XXXX customer service and was told that the card can be used on XXXX and that XXXX is not having issues with fraud. The issue is that Amex gift card is blocking payment for some reason. 

Amex gift card customer service told me to try other merchants, so I did. XXXX also didnt work. Neither did XXXX. Both are huge sites Ive successfully ordered from many times. In fact, the {$1000.00} I sucessfully spent of my {$1500.00} Amex gift card was a XXXX purchase ( {$1000.00} XXXX gift card ) and that went through with no hassle at all. I never expected my cards to suddenly stop working, because prior to this, I never had any problems, including with these 2 specific cards. 

When you call the Amex customer service line, one of the automatic options before youre connected to a human is to hear more information about how the card can be used. There, the voice says can be used everywhere in the US where American Express is accepted. This used to be the case, but definitely isnt true anymore. 

XXXX and XXXX from Amex customer service both told me to send an email signed with my name XXXX that says the provided case number in subject line. They claimed a refund check for {$590.00} should be delivered in 21 business days. 

The check never came, and after a month, a different customer service representative said both XXXX and XXXX were wrong, and Amex doesnt refund gift cards. 

Many Amex customer service reps claimed the issue was vague security issues with the merchants and that Amex automatically blocks the charges for security purposes because of security issues on a long list of hugely popular websites, including XXXX, XXXX, and XXXX. This means that Amex gift cards are now essentially useless, because its impossible to know what sites wont be blocked, and it doesnt make sense that so many prominent and widely used sites are blocked automatically. 

The bottom line is : I tried customer service, I tried multiple major sites, and I tried to get a refund. Im now out of options and it feels like Amex just stole my money. What can I do about this?