If you are including more than 1,000 products in the report, you may be affected by bug 65253. Any eCommerce reports that report on products (such as the inventory report and summary report) will fail if more than 1,000 products are included in the report. Our engineers are working to change the report so that it will bypass this constraint, but until that time the best work-around is to just run the report multiple times. As long as you include fewer than 1,000 products in the report it should run fine, so if you are trying to report on a store with more products than that, segment the products into smaller groups and run the report once for each segment. So for example, if you have a store with exactly 1,000 products and you are trying to run an inventory report, run the report once only looking at the first 500 products, then run the report again only selecting the last 500 products. The two report files can be combined together in Excel if needed.

Please contact support if you would like to be notified about progress on the bug or would like assistance with the work-around.