I had this happen with American Express. Went to two stores in a row where the chip failed and I had to use a different card. Went online to request a new card and they sent one out immediately with no charge or really any questions (I think I did say that the chip stopped working, but that was it).

Later, before the new card arrived, I tried using the old one again and it worked, so I just chalked the whole thing up to those two stores likely using the same payment processor that was having issues that day or something.