Something strange has happened to the credit card system, and I can't think what the cause might be.
From the 8th October, the number of credit card declines that I'm getting, has roughly doubled.
You get a decline when there isn't enough money in the card you're trying to bill, or if you got the expiry date wrong, or if the bank just feels like declining it. That last category includes:
Bank is worried about the billing coming from a foreign country
Bank is concerned that the billing is far from the usual pattern of spending
Bank just declines one in twenty billings, just to show they care.
Bank declines the billing for no reason that anyone can discover
I don't know what's caused this recent increase in declines.