Hi Robert,
Handling the "add to cart" event is actually taken care by Virtuemart Core. It has nothing to do with MaterialMart (unless MaterialMart breaks the flow)
Are you experiencing the same issue on the MaterialMart live demo?
demo.flexiblewebdesign.com/materialmart/index.php I highly doubt so. Something must be wrong specifically to your website. I am happy to assist you to find what goes wrong though.
Can you try to temporarily disable MaterialMart from your website and run a benchmark test to see whether the problem is related to MaterialMArt or now?
To temporarily disable MaterialMart, follow these 2 steps:
1- Rename this folder:
/template/YOUR_TEMPLATE/html/com_virtuemart/ to
/template/YOUR_TEMPLATE/html/com_virtuemart2/
2- Unpublished this plugin: "
Flexible VM3 Template"
Once you do these 2 simple steps, you will notice, MaterialMart is completely vanished from your Virtuemart Pages. Please try it, and check whether or not you still have the add to cart problems you mentioned. If the problem vanishes, then it must be caused by MaterialMart and i will be happy to assist you to resolve that problem. Then, please provide me your website URL and let me take a look.
Regards.