sorry, but you have chosen to work with a 2 year old version, while (it seems) updating WP.
the plugin gets updated not only to add more features but also to fix bugs and make it play nicely with new versions of wordpress.
if you do not update the plugin but WP only, you run the risk of things breaking. there isn’t anything i can do there.
that said, because you have not updated, the most likely problem is your db is using an outdated scheme/collation so you should fix that (see here https://support.wp-pizza.com/topic/error-sorry-we-could-not-find-this-order-2/)
regarding your install trying to connect to root: this has nothing to do with the plugin but is somewhere in your setup