How to make permalinks on a site that uses WPML work on domain alias

Hi,

We have a main domain for our Spanish users (let’s call it: dominio.es).
We installed WPML in the main domain and it is set so all the Spanish pages are viewable at: dominio.es and all the English pages can be visited on dominio.es/en

Then we bought a secondary domain to be used as Alias for our English users (let’s call it: domain.com) and added domain.com on Plesk as an Alias of dominio.es

The Spanish URLs work perfectly.
Meaning that dominio.es/contacto and domain.com/contacto both display our Spanish Contact page.
But it isn’t the case with the English pages and unfortunately domain.com/en/contact shows a 404 Page Not Found error instead of the original English contact page that we have at dominio.es/en/contact

I guess we have a conflict with our permalinks and the way WPML generates the pages within the English folder but I can’t see how to fix it.

Keep in mind that my domain alias doesn’t have a hosting space in Plesk so I can’t upload anything to it.

BTW, I’d appreciate it if you can tell me of a better way to have one only WP installation serving 2 domains for 2 different languages and audiences.

Kind regards,

Jose