Update June 27: A new update from Google has apparently led to select Chromecasts not working. Google is suggesting users reboot their devices, and notes that an upcoming fix will solve the problem if a reset doesn't work.
Sometimes, even the best devices hit irreparable snags. But before you hurl your Google Chromecast into the nearest star (or send it back for a replacement), you may want to try restoring the device to factory settings and redoing the setup process from scratch. The process takes only a few minutes, and you can do it even if your computer doesn't recognize your Chromecast.
To start, your Chromecast should be hooked up to your TV and connected to the same Wi-Fi network as your computer.
For Modern Chromecasts
1. Open the Home app on your smartphone. This is the app that controls your Chromecast.
3. Select Factory reset from the menu. Once again, tap the vertical ellipses in the upper-right, and you'll see the option.
4. Confirm your choice. Once you select OK, the Chromecast will reset, and you can try setting it up again from scratch. Hopefully, that will solve any problems you've been having.
For Older Chromecasts
1. Open the Chromecast app on your computer. The location of the Chromecast app can vary, but if you installed the program recently, it's probably on your desktop. If not, check the Start menu, Applications or the directory where you installed it (depending on whether you are using Windows, Mac, ChromeOS or Linux).
2. Click Settings. If you have multiple Chromecasts on your network, be sure to select the one you want to format, and leave the other ones alone.
3. Click on Factory Reset. Don't click on this unless you're absolutely certain you want to go through the Chromecast's initial setup process again.
4. Click on Reset. The Chromecast will now reset to factory settings, and you'll be able to restart the setup process. If problems persist, contact Google, as your machine may be defective. If this process worked, you're done. If not, read on for one final step.
5. Press and hold the black button, if all else fails.If you can't get your computer to connect to the Chromecast, you can still factory reset the device manually. Right below the microUSB port, there is a small black button. While the Chromecast is hooked up to the TV, press and hold the button for 25 seconds. When the light next to it begins blinking, you can let go. After a minute or two, the device will be reset, and you can try the initial setup process again.