Someone posted in another thread that the latest update to ShowBox caused this behaviour. They mentioned there was a possibility to uninstall MX Player, install an app which pretends to be MX Player, which then re-allowed opening the video stream in different apps. The website where the data is streamed from have added something to the HTTP header or MIME encoding (or something similar?) which breaks the previous behaviour of being able to use external apps.
Another approach would be to go to Android's Settings (if you see a colourful interface, first click the last tab on the right, then the More Settings button). Click on the Apps entry, scroll on the right down to Show Box, and select it. There should be a button that shows something like Uninstall updates. Revert back to the original app version, see if the older app still handles this newer system.
Another approach would be to go to Android's Settings (if you see a colourful interface, first click the last tab on the right, then the More Settings button). Click on the Apps entry, scroll on the right down to Show Box, and select it. There should be a button that shows something like Uninstall updates. Revert back to the original app version, see if the older app still handles this newer system.