try manual installing by clicking the download tab, scroll down to manual zip file click it, then click the version you want, download and extract the folder out of the rar file and put it in the versions file by going to the windows search bar and type run, click run and put in the bar %appdata%\.minecraft\versions then click the enter button on keyboard then put the aristois download folder in versions, goto the minecraft launcher and click installations, then click new installations and change the versions by clicking latest release and choose the aristois version and click create and play on that installation and done no problemo if it helped.
