For years we've distributed to our entire emailing list coupon codes good for a few days of free shipping with $50 purchase. All recipients are in the USA or territories.
Over the last few months we've heard from several customers who received a warning while attempting to check out saying the coupon offer is "not valid for the zip/country being used." These customers were in several different states. Perhaps 2% of coupon users encountered this problem. The code works fine for the rest.
Neither we nor our host, Lexiconn, is able to replicate that problem even entering the customer's exact order.
Any idea?