When you want to save the Sheet as PDF all the images show up in the preview but not in the downloaded file. That is because the images inserted in cells are not embeded in the Sheet itself.
To solve this please do the following:
1. Please make a duplicate of the Google Sheet with File>Make a Copy – don’t skip this step*
2. In the copy file open FileDrop>Settings>Export Sheet as PDF
*the export process will embed the images in the cells, this might not be desirable and it cannot be reversed.
The function will export the current Sheet and might take a while, it might fail if there are many images. You can also export only selected cells.
If you have multiple sheets in the Google Sheet you must export each one at a time.