This is probably obvious and old news but I have found that at least a couple of occasions a parts supplier won’t accept an order if the IP address through which the order was placed was foreign, generally due to a VPN. It doesn’t matter if the credit card and shipping addresses are U.S. or if you are a repeat customer. So seems like one needs to turn off VPN tunnel (or ensure it is from U.S.) when ordering parts. The explanation I hear is that it’s an ITAR issue (which I get), but I would have thought that in today’s world where internet traffic can route from anywhere that foreign IP address alone wouldn’t be the deciding factor. But maybe I am naive and misinformed.