For me it opens just fine in Excel 2016 image.png (44.9 KB)
Excel Leave Tracker 2021 Hidden sheet.zip (41.2 KB)
I added the file once more. If it still does not work, I’ll try if can get the same problem with a different file.
You were right when saying that the issue is related to hidden worksheets. We have found the issue in our code and fixed it. The fix will be included in the next public release that is planned for the middle of September. We’ll notify you here when the new version will be available.