Left Sidebar disappears on Category page

Hi,

Apologies for what may well be a stupid question but I have been trying to no avail to get my left sidebar to appear on my category page.

It appears correctly on all of my posts and pages example below:

http://www.freebetdeposit.com/ladbrokes-50-free-bet
But no on the catgory page which I have set up as a menu item to capture all of my posts where it disappears, As you can see below

http://www.freebetdeposit.com/free-bets/free-bets

I have tried loking at other posts and tried changing setting and editing css files only to break my site twice. So I am wary of changing the css files with my limited knowledge. Is there some simple setting I am missing of someting I can put in the Child Theme?

Many Thanks for any assistance given and apologies if this has already been covered.

Chris