Invalid credit card?

A couple of days ago, I attempted to buy a book with my new Amex chip and pin card. First of all, the machine wouldn't recognize the card so the shop assistant rubbed the chip on her clothing, presumably to clean it. Eventually the card was recognized and I typed in the pin. The card was declined, no reason given but more about that below.

But no matter, out came the Mastercard. This produced a round of the machine not recognizing the card and chip rubbing. But to no avail. At this point, I suggested that there might be something wrong with the chip reader. "It's 14th February, so I can't accept a signature" said the shop assistant. Although this was not true, I didn't argue but produced my old, non-chip Amex, signed and bought the book.

So why was my Amex chip and pin declined? Perhaps I typed in an incorrect pin? Or maybe it was because the start date of the card, according to the little report slip, is 1st March, two weeks in the future. If that was the reason, then why have I been able to buy goods with it in other places? Do some systems ignore the start date information and allow purchases with an invalid card?