MarketPress is not adding products to shopping cart

This is on a multisite install, it was working fine, now it stopped adding items to the cart. I tried on another dummy site on the same network and it worked fine. The site is and the cart is on

This is time sensitive since it was working and we were about to launch the site, but it stopped working.

The only modifications I have made to the plugin were to the language files to “improve” some of the spanish translation and to finish localizing some aspects that weren’t localized. Other than that I have made no changes to the plugin. I have also re-installed it fresh from scratch overwriting my language files and that made no difference. I also deleted the DB entries for mp_ and then totally fresh installed again and it still is not adding products to the cart.

I have some JS running on the site and I also disabled that and still no luck.

Any help would be appreciated and I would gladly pay for someone to take a look at it if it is beyond the abilities of the support forum to fix.

Thanks Much!