You do not have a product in the API issuance - it does not add a supplier record.
They may not have anything to do with CRM, but they could explain why the product is not in the search results according to your access.
Is there a restriction on categories for access on their side?
PS: I sent you an archive with a log file to
zb@ukr.net - where we knock and what we get in response - you can provide Brain as an example that there is no issuance of the desired product in the API - let them give an explanation why at least.