This was posted on Oculus forums about 15 mins ago. Out of date certificate is the cause.
Hey everyone – This is an issue with our software certification that we’re still actively working on. 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.