Reviewing all settings in Settings>Checkout. I don't see any issues here, or anything I can attempt to turn off/on.
I've tried creating a new gift card product from Products>Gift Cards> Add new gift card product. I still get the same behavior with the default settings of a new gift card product (i.e. not tracked, uses gift card template, etc.).
I've review the current gift card for Product-related settings. It does not track inventory so I can't understand why it would show up to a cart checkout routine as "out of stock".
I've tried looking in the theme.liquid and cart.liquid files and I don't see a checkout routine to view/investigate.
Hey, I just went through the same issue. I think it is because I manually added a Variant to the "Gift Card" product via "Products", rather than going through the "Gift Card> Add a Gift Card" method. After I did this, my gift card product started showing the out of stock.
I looked through shopify docs but was unable to find a way to actually update an existing product to add more variants:
While it says "update" is an option, I was unable to do so.
To resolve the issue on my end, I recreated the gift card product with all the "Denominations" I previously had, plus the additions I was looking to make in the first place. I tested this out and it no longer has the Out Of Stock issue at checkout.
I then moved the old one to "Draft" status and renamed it with an "- OLD" at the end of the name. Not sure if this is necessary but instead of deleting the product entirely, I wanted to ensure that the customers who bought these would still be able to use it.