As long as a product is marked in stock, buyers can place orders and your affiliate links can convert. It doesn't guarantee a large amount of inventory: stock can be low, even just a few units.
Why stock matters before you promote
If a product goes out of stock, your videos still collect views but won't convert. Check stock before promoting, especially when demand is rising and inventory is draining fast. Going out of stock is also one of the reasons a product link can disappear from your video entirely.
Next steps
The consequences and the checks: