MV files won't play

Movies that I take with my camera have always played. Now suddenly they won't. I checked file defaults and there is no file to associate. It just wants me to pick a program from the store... and pay. I know I have programs installed that can open these files... how do I assign one of them to MV files? When I click the plus sign it just takes me to the store.

Looking at the screenshot you need to select the .MV extension in the left column and then the right column should show all apps that can open them, pick the app you use

Alternatively you should be able to right click a file in explorer and select open with, this will then set that program as the default

That worked, Thank you!

Glad to hear that it worked