oh no, did it say like "Windows protected your PC" when you try to open it? if so I believe there's a "show more" button (or worded similarly) and when you click it you can choose "run anyway"
Huh how strange, the only thing I can think of is moving the folder to your desktop (if you were trying to open it out of downloads) and trying to open it there, or open as administrator? Otherwise, on the next build I'll check the signing information, due to time this build was pretty rushed