Seems like as a result of a technical issue, all the Oculus Rift headsets have stop working. If you are not able to start your Oculus Rift, it is because of a expired security certificate. Here is what the company says about the problem:
For security, we use a certificate to ensure that the software you receive actually comes from Oculus. That certificate has expired, and we’re looking at a few different ways to resolve the issue. We’ll update you with the latest info as available. We recommend you wait until we provide an official fix. Thanks for your patience.
Another update says there is an Oculus software update in place that fixes the issue where Rift may fail to start up. For more info and instructions, you can visit here. According to the feedback, Oculus Rifts are coming back to life, thanks to the update.