I see the TEST word in your code, but I don't see that anywhere in the output on
123.socialapp-store.com/home/product/view/3/8
Do you see it on that page? If not, that means that the lines you put that code in are not being executed (likely because the if statements above it aren't true). Since it's not showing, that means our {SCOpenGraph image=xxx} tag isn't being output either and would explain why the image isn't showing.
I see multiple other img tags in the code you posted above, like:
<img id = "main_image" ...
My guess is that you're not putting the {SCOpenGraph image=...} tag in the right section.
Thanks,
Alex