Affirm showing on some product pages but not all

I have Affirm configured to show on product pages. It shows on some product pages, for example https://superscoots.ca/product/fighter-11/ and https://superscoots.ca/product/teverun-tetra/ but on others it does not appear (for example, https://superscoots.ca/product/fighter-supreme-2/ and https://superscoots.ca/product/fighter-supreme-plus/).

All products are quite similar—same category, similar prices (all between $50 and $30,000) and all use the same template. Why does it not appear on some product pages?

The page I need help with: [log in to see the link]