There was an unfortunate email glitch where if your username was already present in the instance, it would silently deny your application, and the beehaw admins would be none the wiser. See https://beehaw.org/post/562922
Additionally, there has been some issues with the beehaw's email provider that has recently been fixed and the backlog has started to decrease. See https://beehaw.org/post/604680
Also, ML is just statistics and calculus.