Rae from Shopify here. Thank you for reaching out about this.
To confirm, when creating a checkout link for specific products, are you following the steps listed here? Or, are you creating a manual checkout link by following these steps?
The format of your link looks slightly different than the expected format, which should include ‘?channel=buy_button’ in the URL.
However, once I have more information on how you created the checkout link above, and which steps you followed, I’ll be happy to help further!
Do you still need help with creating a checkout link? If so, please feel free to reply back to me here with the information discussed above, and I’ll be happy to continue helping out.