WeChat Pay accepted my Visa at FamilyMart, but not at a hospital kiosk

Short field report from Shanghai. My overseas Visa through WeChat Pay worked for FamilyMart, Luckin, and the metro QR code. It failed at a hospital self-service kiosk and at one older restaurant QR code.

Cash solved the restaurant. The hospital desk accepted the same card through a staffed terminal.

The pattern seems to be merchant type and terminal age, not the card itself.