I am using Crouton with Ubuntu 14.04 on my Acer Chromebook 15.
My Chromebook was working perfectly fine before I turned it off. Here are the changes I made: I updated chroot to the latest version, installed steam on Wine/PlayOnLinux, and installed a game to a USB Flash Drive. I tried playing that game, but it wouldn't even boot up. I then restarted my computer. When the Chromebook powers on, it tells me that Chrome OS verification is off, so I press Ctrl+D (like usual). But after that, it tells me that Chrome OS is missing or damaged.
What could be the problem here? Is there any soft way to fix this, or do I need to hard reset Chrome OS?
Use the Chromebook Recovery Utility to create recovery media for your Chromebook. Then follow the steps mentioned in Recover your Chromebook guide.