Repair a wordpress / optimizepress / woocommerce issue URGENT!

I have an urgent issue which needs resolving. A sales funnel has been made in Optimizepress which allows us to add to cart directly from a sales page and move on to the next page in the funnel. This was all working fine but has suddenly started adding the product twice. This may be an SSL issue, I have tried what I can. I have noticed that the problem doesn't happen on firefox on my computer but it does on others as well as Chrome and IE. I need it to work on all browsers, obviously. Ideally I need someone who is already competent in the plugins being used who can start immediately and won't stop until the problem is resolved.