We have found that sometimes the Safari browser (and occassionally other browsers) will decompress the OptimizePress zip file downloads when you download them from our members area
To stop this happening, when you download from our members area, right-click the link and select “Save Target As / Save Link As” and ensure that the file is saved as a zip somewhere you can find it on your computer
Alternatively, once you have the folder/file on your computer you should be able to right click and create a zip file from it by choosing an option like “add to zip” or “Compress folder”