OK, it turned out to be my card.

Went to another ATM, never offered DCC but it did say transaction canceled, contact your bank. Got the same thing on two ATMs outside a bank.

So I opened the Schwab app on my iPhone, to see if I could message them. Digging around the menus, there's a "Manage Your Cards" option and my card tied to my checking account was set to Locked.

Never seen this option. May have come in some app updates at some point. I hadn't used it at an ATM since end of July or so. Been using the card for years, often checking the app to see how much they withdrew from my account.

Maybe I did lock it and forgot about it, though honestly don't recall seeing it before.