Make sure that you have the updated Adobe Camera Raw installed. Your camera requires ACR 14.4 which is the latest available with Elements 2023. In the Editor, go to Help>About Plug-in>Camera Raw and confirm that you have the correct version. If not, also in the Help menu, click on Install Camera Raw.
If you are talking about the Adobe Photo Downloader, this is a problem that seems to be random and may depend on the number of images on the memory card and or other camera and computer resources. Sometimes, if you wait a while the thumbnails will appear. IMO, it's not worth waiting. Simply download the photos and sift your photos in the media grid.