What I suggest you do if you want a mobile.domain.com type site is install another add-on mine -
https://vborg.vbsupport.ru/showthread.php?t=174381 - after installing this, configure it for mobile.domain.com, also add mobile.domain.com to your post referrer whitelist in Admincp->Settings lastly, configure the sub domain in cpanel to not redirect, but to park it on the same websapce as your primary domain.