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.
OnePlus 5T review: Hands-on
See the Best Button Badge Designs of 2017
iPhone X review
Black Friday 2017 : date, sites participants & bonnes affaires