We are investigating why the gateway is null when retrieving that data using the Abandoned Checkouts API, even though the timeline on the “Abandoned Checkouts” page contains payment information.
Also, although it was taken normally until February 2022, gateway seemed to be Null from March 2023 onwards.
If anyone has any idea, I would appreciate it if you could give me some advice.
reference
https://shopify.dev/docs/api/admin-rest/2024-01/resources/abandoned-checkouts#resource-object