Why does an inventory product with stock on hand not appear when you add material or click Replace Product on an invoice? If the product shows its quantity on the Product Stock page but you can't find it in the Materials list (the Add Products From List dialog) or after clicking Replace Product, check its Dropped Date: a product with a Dropped Date set in the past is hidden from both.
Why This Happens
This section explains why a product with a past Dropped Date shows on the Product Stock page but not in the Add Material and Replace Product search.
Add Material and Replace Product both open the same product search list, so the same rules decide which products appear in either one. A product whose Dropped Date is in the past does not appear in that search. The Product Stock page works differently: it still lists a product with a past Dropped Date, along with its stock quantities, unless you turn on the filter that narrows the page to dropped (expired) products. To open the Product Stock page, go to Inventory Products in the left menu, then Product Stock. It also appears under Warehouse, then Product Stock.
The confusing part is what the search shows you. When the only matching product is hidden, the search list shows "No data available." with no note that anything was filtered out, so the product looks as though it doesn't exist at all.
How to Fix It
To make a dropped product appear again in Add Material and Replace Product, clear its Dropped Date or move it to a date in the future.
In the left menu, go to Inventory Products, then Product List. Find the product you're trying to add and click the edit icon on its row. The product opens in an Edit Products dialog.
In the Edit Products dialog, find the Dropped Date field. It sits below Collection and above Effective Date. Clear the Dropped Date, or change it to a date in the future.
Click Save to save the product.
Return to the invoice and open the product list again. To add material, click the green Add Products From List icon, which opens the Materials dialog. Tick the row for the product. The Add Materials button stays greyed out until a row is ticked, and then you can click it. To swap a product that is already on the invoice, click the Replace Product icon on that product's row, which opens the same list with a Change Material button. The product now appears and can be selected.
If It Still Doesn't Appear
If a product with stock on hand still doesn't appear in Add Material or Replace Product after you clear the Dropped Date, check these two settings on the product record. Either one also keeps a product out of the Add Material and Replace Product search.
Discontinued Product: if the product is marked as a Discontinued Product, it does not appear.
Visible: if the product's Visible setting is set to No, it does not appear.