iCloud Photo Upload - which file type does iCloud/iPhoto not support?

I recently exported 28,000 photos & videos spanning 15 years from Google Takeout via an app called Google Photo Metadata fixer (so that the metadata is exported from Google) with a view of changing provider to iCloud/iPhoto for ease.

The files take the following file types: GIF, HEIC, JPG, MOV, MP4, MPG, MTS, PNG, WMV, M4V. When I select all 28k photos/videos and upload to iCloud photo, only 17k upload. Which of the following are not supported via iCloud/iPhoto please?

Thanks!