400
merchants.invalid_cursormerchantsThe cursor is not an RFC 3339 instant
Returned by the implementation; no specification rule declares it yet.
This listing's cursor is a timestamp, and the value sent is not a valid RFC 3339 instant.
Why the API refuses
the cursor is not an RFC 3339 instant
What to do
Pass next_cursor back unmodified. Constructing one by formatting a date yourself is what produces this — the format is 2026-10-01T09:00:00Z, but relying on that is relying on an implementation detail.