[Quoth]

I'd not heard of it with B&N, but common with Amazon in UK. Not heard of it here yet.

This can also happen with Amazon (and you lose your Amazon Library and publishing if using KDP) if you make "too many" returns. There is no T&C explaining how you might violate their rules nor appeal without legal recourse. There is also a massive issue with parcel fraud in UK. Amazon, not you, is responsible till you get it, but delivery signatures / advice is being forged. Amazon tells people to take it up with carrier, but legally, almost everywhere, that's their responsibility.

Google can block your account from purchasing and/or redeeming Gift cards, though unlike Amazon everything else works. Separately they can ban people from gmail (which might since Jan 2024 mean being unable to send to any gmail address if your alternate email doesn't have two kinds of security. This applies now to everyone). Google won't explain why an account is blocked from purchasing.

So Barnes & Noble isn't unusual. There are plenty of international online sellers or services that are problematic. Paypal blocking people from taking money out of account (like a charity or a developer accepting Paypal donations). Ebay can be inexplicable.

Big corporations seem to think the only rules or laws that count are where their HQ is and that benefit them.
X, the artist formerly Twitter, is in dispute with EU and Musk with US SEC over Twitter purchase.