Hi,
I checked your website and like you said if we choose product meta to display it won’t save that option.
I notice that you have 33 active plugins and a lot of Woocommerce plugins. In my opinion this probably is a plugin conflict of one of those plugins.
Deactivate all the plugins and check if you can activate the product meta option.
If the result is positive, you will have to activate the plugins one by one until find out what plugin is causing that.
-Rui