Filemaker Pro 11 - Inventory update issue

i need some advice on Inventory Control within a FileMaker Pro 11, starter solution.

We are using "Invoices" (one of the standard starter solutions) and the inventory update button is no longer working. It has changed from a mid/dark blue colour to a light blue colour. At some point during importing our cutomer and product information I must have changed some of the relationships. I need advice on how to get the invoices to update the stock totals.

I am physically located in Cheltenham, Glouestershire.