Microsoft limits the Insider program, you can not install Windows 10 betas if you have old versions of the system
Microsoft wants to better coordinate the way in which the preliminary versions of Windows 10 are installed within the Insider program, and therefore from now on will not allow the older Windows 10 builds to update directly to the latest ones.
This means that if you do not have at least the Creators Update installed you will not be able to join the Insider program , in fact, even if your Microsoft account is already registered in the program you will not be able to install anything before updating to the latest stable version.
This is not the same as the “Skip Ahead” mode, in case someone gets confused. For example, having the latest version of Windows 10 today does not guarantee you can try the first Redstone 5 builds .
The Insider program has several update rings : the slow one, where less updates are received and the new features that have been tested for a little more time are obtained; the fast one, which offers you the possibility to first try all the new Windows 10, and finally “Skip Ahead”, a limited space that lets the Insider “jump” to the next version before the previous one is published, as in the case of Redstone 5.
If you are part of the program or not and regardless of the ring you are in, if you have not updated at least the 1703 (Creators Update) for any reason, now you must do it manually before you can install any recent build .
Microsoft recommends doing so using the Media Creation Tool . Once updated, you can go back to the Windows 10 settings to join the Insider program.