The file association has gone missing I reckon.
Shift + right click on an mpeg and select Open With from the pop-up menu. Select your preferred player from the list presented and make sure the box "Always use this program..." is ticked.
Samsung Galaxy S8 review
1995-2015: How technology has changed the world in 20 years
This poetic animation about monsters is illustrated in a Van Gogh painterly style
How to get WWDC 2017 tickets
Synology invites you to visit them at Insomnia on 26th – 29th August. Book your tickets now and visit Synology.