Same thing happened to me. Its supposedly meant to prevent credit card fraud. When adding funds to your account from a new credit card you have to wait seven days to make sure it is indeed your credit card, verifications are made during this time. However, even though i used the same credit card ive been using for a while now, i still get the same thing every time. I saw something on the market this afternoon and wanted to buy it, as it had gone down in price a lot. But when i added my funds i now have to wait seven days and the prices will probably go back up again. In my opinion this block shouldnt even exist.