My site on Chrome in Android won't scroll. It's not related to the chat plugin as we have had the problem without any chat plugin, a different chat plugin, and the current chat plugin.
With Samsung native browser the site will scroll. It seems to be a Chrome / Android issue.
in your style.css, ..
padding-right: 0px !important;
overflow-y: hidden !important; /* this is removing the scrollbar */
try removing this first... to debug...
As I see it, nicescroll plugin is not working well on mobile. might as well just use this plugin on desktop version.
This fixed it.
The issue is with a conflicting plugin as the author's demo site seems to be working fine.
If I was to have a gues I would say its probably the lightbox plugin but I could be wrong - you should start troubleshooting by deactivating all active plugins, refresh the site to see if the issue has been resolved. You would then proceed to reactivate the plugins one by one while checking the site till you find the conflicting one.
The conflict may not necessary be with a plugin versus the theme - it could two plugins which a conflicting and therefore causing the issue.
Hope that helps you in getting to the bottom of the issue.