Products not found by Shopify Buy Button after CSV import

Hi,

I have a serious problem when trying to use Buy Button. I imported ~50 products from another shop, as a CSV file. When trying to fetch any of these using the Buy Button library, I get the following error:

When creating a new product in the same shop and creating a buy button using its ID, it works just as expected.

I have double checked the shop URL and access token used to initialise the client. I have no idea why this is happening, I’d greatly appreciate any help.