Do the following steps to troubleshoot the issue:
- Close all Steam apps on your computer, including the SteamVR app.
- Unplug the link box cables (HDMI and USB) from your computer, as well as its power cable from an electric outlet.
- Wait for a few seconds, and then plug the cables back in. On your computer, you might see a notification that drivers are being installed. Wait for the installation to finish.
- Restart the SteamVR app.