Is it marked for purchase and has an account associated with it?

Why does this happen?

In QuickBooks, you can have non-inventory and inventory items. If your items are marked as non-inventory then they cannot be placed on purchase orders.

How do I resolve this error?

Here are the steps:

1. Log into QuickBooks.
2. Go to the gear box and click products and services.
3. Edit each product.
4. Mark it as purchasable.
5. Ensure it has an inventory asset, a cost of goods sold, and an expense account.