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 embedded in the Sheet cell 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>Click the Embed Images in Cell button
*the embed process will embed the images in the cells and you can download the sheet as PDF with the images in the cell.
The function might need to be repeated if there are many images and depending on the type of Google account you have (free accounts have a limited processing time). The process restarts where it left off.