Earlier this summer, Microsoft made a decision to split the Windows Insider build into multiple branches. This is a common practice in software development when one branch is reserved for an upcoming release and another branch will diverge and continue development for future releases. Windows 10 team did this so they can get ready for the Fall Creators update for Windows. Since most of the features that will be introduced in the Fall Creators Update were already shipped in the preview build months ahead. As the team is getting ready for the next major release after the Fall Creators Update they created a separate branch. Microsoft calls it “Skip ahead to the next Windows release“, this will be the channel Microsoft to release the greatest and latest Windows 10 Insider Preview. If you have not opted in “Skip ahead” to receive build updates you might be too late and will find yourself unable to enroll in this branch.