Just started today the back button on Chrome on a Samsung Chromebook doesn't work on this site. The only way to go back is click on the Forums at the top of the web page.
Maybe something updated on the Chromebook or the site.
Are you referring to the backspace key on the keyboard, or the left directional arrow on your browser? Google disabled the use of the actual physical backspace key while in Chrome some years ago. Apparently, too many were complaining that they lost whatever they were doing when accidentally hitting this key.