WooCommerce products showing “Out of stock” message when not actually out of stock

I had this same problem and I think I figured it out. I used the CSV Import/Export suite to export all of my variations. You’ll notice that stock is set to 0 when it should have a value of null.

You have two options here:

1. Go into each individual product, click the variations tab and expand each variation – unchecking the “manage stock” checkbox:
2. You can do a find-and-replace on the database substituting the 0 value for null.