When I double click on an mp4 file, vlc does not open it.
mp4 are set to open with vlc.
Open with vlc does not work either.
I have to open vlc and then play it from there?
Possible Bug ?
May I ask that you confirm that your issue was/is resolved, that you can set VLC as preferred application for mp4 and
- double-click on mp4 opens VLC, and
- right-click "Open with" VLC works as well, and
- those both work for you in your currently installed release (please provide that release version for confirmation the resolution is "persistent") ?
The issue was resolved. My post was 6 years ago. 
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