Fix the "Chrome OS is missing or damaged" error with the Chromebook Recovery Tool

If this error appears, your Chromebook's operating system isn't working properly, and you should recover your Chromebook.
Because recovery reinstalls the operating system to get your Chromebook working again, it will also permanently erase all information on your Chromebook's hard drive. If you've saved your documents to Google Drive all of it has been safely backed up for you.
In the steps below, you'll create recovery media and go through the recovery process to fix the error.
What you need to get startedBefore you get started, you'll need:

• The Chromebook with the "Chrome OS is missing or damaged" error
• A different computer with the Google Chrome browser installed (Windows, Mac, or another Chromebook)
• An SD card or USB drive that you don't mind erasing
• The Chromebook recovery app (details below)

What you need to doTo recover your Chromebook, you'll first create media with the Chromebook recovery app, then reinstall your damaged Chromebook’s operating system.

1. Install the Chromebook Recovery Utility on the working computer (not the Chromebook with the “Chrome OS is missing or damaged” error).
2. Open the app and follow the on-screen instructions to create the recovery media.
3. Insert the SD card or USB drive you’ve created into the Chromebook you want to recover.
4. Follow the on-screen instructions.

https://support.google.com/chromebook/answer/1080595?hl=en&source=genius-rts

https://chrome.google.com/webstore/detail/chromebook-recovery-utili/jndclpdbaamdhonoechobihbbiimdgai