I will add that one of my debit cards requires it to be firmly held into the ticket machine until it says to remove it, so give that a go if the machine is having an issue with it.
This causes no end of faffing and bother at a number of stations, not least some major ones like Gatwick Airport, and apparently it's all down to trying to help the environment by printing cards on different types/thicknesses of plastic, but the card slots don't accept them unless you force (and hold) the card into the reader, as they're the wrong size.
Unfortunately one has to draw a line with this sort of thing somewhere, and I think this scheme, commendable though it may be in motive, stepped over the mark somewhat!