An eBay listing number from another workflow is not automatically the REST item ID expected by the Browse API. In the eBay integration discussion, name the identifier's source and whether the listing has variations.
eBay's inventory discovery guide explains the distinction and the getItemByLegacyId path for resolving legacy identifiers.
Test a listing with more than one selectable variation, then confirm that the returned item matches the intended selection. Do not silently substitute the first variation when the integration lacks enough information to choose one.
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