This is a super easy fix. You need to un-check "track quantity", under the product. The products will show up as "sold out", when the products inventory is set to 0.
If you found my reply helpful then please Like and Accept Solution.
Feel free to email me at firstname.lastname@example.org
Raquel Marie: Shopify Development & Conversion Expert | Shopify Theme Customization & Development | Shopify Design | Conversion Design