When you upload an Excel spreadsheet to the Bulk Product Editor the app will automatically choose the first sheet in the workbook to use. Previously this could lead to a hidden sheet being selected if it was in the first position in the workbook. We saw this will working with some other tools that would automatically insert an hidden sheet at the start of the workbook when you export data.
Now the app will ignore hidden sheets and instead choose the first visible sheet of an Excel workbook. This should cause things to function as expected, the first visible sheet in an Excel workbook will be the one the app uses.