Hey!
I found the “root” of the problem, or at least more information in case you want to debug (i can still send you details for loging in, but with this info you might sya oooohhh i know what it is XD)
So your plugin works fine as long as the url is like:
DomainA.com
or
DomainA.com/test/
But it fails when it comes down to pass urls such as
DomainA.com/checkout/?lang=es
In this scenario, the only option left is to add every page that contains ?lang=XX as in:
DomainA.com/chekcout/
This way it will work having both added (main domain url and specific checkout url)
Does this help at all?