Latest versions I believe – Upcoming Product v1.5.8.1 and WooCommerce v3.1.2
Unfortunately I can’t direct you to the website as I don’t currently have any upcoming products! But what I did find was this:
I have 4 products in a category. Products 1 and 2 were available, 3 and 4 were upcoming. Product 4 was the one not showing the “Select Options” link. When I made product 3 available to purchase, product 4 started working properly like the others.
Steve
