Microsoft has today announced that they are temporarily halting Windows 10 PC Insider Preview build availability as they begin to switch their updating systems over from the old delivery method to the new Unified Update Platform.
What does this mean, exactly? Well if you're an Insider and you're not running the latest Insider Preview build, you're now going to have to wait a few more days before you can download it as Microsoft is no longer offering builds on the fast and slow ring.
From the Microsoft blog post:
UPDATE 12/2: We are getting ready to start releasing PC builds to Insiders using UUP. To prepare for this, we are going to pause all PC builds for both the Fast and Slow rings starting this evening (Friday 12/2). We will begin flighting the latest builds via UUP starting with our internal rings first then to Insiders based on each ring's promotion criteria. We're excited to be able to release builds for PC to Insiders using UUP! Mobile builds are not impacted by this.
It's unclear how long this pause in build availability will be, but considering Microsoft wants to test out their own method internally first, it could be a few days at the very least. Stick to Windows Central for more news regarding the Insider Preview.