Can You Be Rejected for Using a VPN?

Half the stuff that I try to buy online these days is rejected. A lot of time, I don't find out about this until a week later when the company tells me they canceled my order. But now that's probably not just the VPN. It's probably the fact that I'm shipping it to a place that is a public post office box. And so yes, yes, yes,. you can be flagged for using a VPN."