choose option not working on store

I have read the numerous posts in regard to this topic and despite attempting all of the various suggestions to fix the issue, I still cannot make a selection in my store if I have used variable products and options. If I’m quick I can briefly see the option before it reverts to “choose an option. Can anyone assist please. http://www.freereinequestrian.com.au select combo rug xtreme will have options for color and size of the horse rug