Quick summary

Imagen couldn't compress your photos for upload.

How to fix this

1. Install or reinstall Adobe DNG Converter. If your camera is new, update it to the latest version.
2. Create Smart Previews in Lightroom Classic. See this Adobe guide.
3. Clean install your Adobe apps. See this Adobe guide.
4. Open the photos in Lightroom Classic. If Lightroom Classic can't open them either, the files may be damaged.
5. Mac: If this started after a macOS update, go to Apple menu › System Settings › Privacy & Security › Files and Folders, and make sure Adobe DNG Converter has access.