Unable to open a .mov file
I have a macOS Big Sur MacBook Pro and i can’t open a .mov file with QuickTime
Obviously it has some obsolete or incompatible codec which current QuickTime Player does not support.
You can check the codecs with MediaInfo or Invisor and post the codec info here for us to evaluate:
https://mediaarea.net/en/MediaInfo
https://apps.apple.com/fi/app/invisor-media-file-inspector/id442947586?mt=12
Or, IINA and VLC should have no issues with playing any decent new or old codec.