Thanks for the update @josh-square ! This explains my case.
I am passing the Location ID in the Web Payments SDK initialization:
const payments = Square.payments(APPLICATION_ID, LOCATION_ID);
But I noticed I am not explicitly passing location_id in my POST request to the Payments API (CreatePayment).
It sounds like that could be the gap causing the mismatch you described. Am I understanding correctly that adding location_id to the CreatePayment(Payments API) payload, matching the SDK Location ID, is likely the fix?