Eli5: When your credit card doesn’t read at a credit card machine, why does covering it with a plastic bag suddenly make it work?

Question

Had this done multiple time at the register. Card not reading, so the cashier will cover the ribbon or the chip with a plastic bag and YATZEE, it goes through. Why?

In: 407

Answer 1

Highjacking your post for a similar question: I have a contactless credit card, but the NFC function only works if I press the chip super intensely onto the device. Does anyone know the reason for this?