I added a app extension, Checkout UI, but it gets no response to query product variant data. and I can get data in GraphQL center with the same query, variant id is from “extensions.settings.fields”, did I miss something?
In addition, official docs all use JSX, but TSX is now popular. If you modify the code to the TSX version, the query will also become invalid.
Sounds like its going to be something straight forward but annoying.
Try logging merchandiseId to the console, if its empty, then you know there is an issue when you get the value from the settings. It should come from useSettings().
Is there any response from the graphql query? It might be the case that the variable is not published on the Online Store, double check that its published to Online Store.