Why is my Sell Through Rate showing as N/A?

There's a couple reasons this could happen. Sell through rate is calculated as number of items sold in a month/number of items purchased in a month. The two most common reasons you could be seeing that your rate is "N/A" are:

1. You haven't purchased any inventory items during the time filtered. This means the number can't be calculated
2. You've applied filters to the sale detail