Publisher didn't make change to paper and now the paper still has the error
Send the publisher an email mentioning that an error that was detected and discussed during the revision period has crept into paper. Don't attribute blame. Ask politely that the error is fixed.

As noted by C26, errors are common. It doesn't matter if the mistake isn't fixed. But, it will probably bug you if you don't try to get it fixed. (Such issues probably won't bother you after you've published a few more mistakes ;-)