I think this was introduced with the most recent change to the selling plan UI on the product page. The “Only sell this product as a subscription” field does not show if there are no selling plans for that product.
If you:
Create a selling plan and add the product to it.
Tick this option on.
Remove the product from the selling plan.
The option is now not visible, but still seems to be ticked.
This means the product can’t be added to cart and the option can’t be turned off unless you add another selling plan to the product first.
Unfortunately for us, this issue resulted in a fairly scathing review from a merchant who thought we were doing this intentionally so they would keep our app installed. We’ve now had two merchants contact Shopify staff about this only to be told that the issue is caused by our app.
Is it possible to always show this option, even if there are no selling plans attached to the product?
If the “Only sell this product as a subscription” option remains ticked and is not visible after removing the product from a selling plan, you can try the following steps to resolve the issue:
Re-add the Product to a Selling Plan : Go to your Shopify admin and re-add the product to a selling plan. This should make the option visible again.
Uncheck the Option : Once the product is part of a selling plan again, uncheck the Only sell this product as a subscription option.
Remove the Product from the Selling Plan : After unchecking the option, you can remove the product from the selling plan again.
This process should help in making the product available for one-time purchases again.