Problems after Installing on RedShop

I received this error:

Fatal error: Cannot redeclare rsCarthelper::coupon() in /home/multicb/public_html/components/com_redshop/helpers/cart.php on line 3427

I have followed the instructions correctly - so why does this error still occur?

Thanks.

Hello,

What version of redshop is this?

Also do you receive this error after doing a specific action?