Do the videos play in QuickTime Player?
What is the format of the videos? Does your camera support more than one video format?
Photos is working best with videos with codecs HEVC or H.264. To get an idea, which codecs are problematic on macOS 13 Ventura see this list for iMovie: About legacy media in iMovie for macOS - Apple Support
If you can play the videos in QUickTime Player but not on Photos, there may be a problem with your Photos Library. For example, videos may not play, if the Photos Library is on a volume with an incompatible file system format. If your Photos Library is on an external volume, prepare it exactly as described here: Move your Photos library to save space on your Mac - Apple Support. Particularly, a case-sensitive format of the file system can make it impossible for Photos to access the resource fork with the video component in the container of the video.