If your products are not appearing in your Buy Button sales channel, you can easily fix it by following the steps below.
Step One

Go to the product page for the product that isn’t showing up. Go to the column on the right and click on ‘Manage’ beside Sales channels.
Step Two:

In the window that pops up, check the box beside ‘Buy Button’. Click ‘Done’ and then ‘Save’ to confirm your changes. Now your product will appear in your Buy Button sales channel.