The language subdomains stuff requires lot of requirements in your server to make it work.
The instructions are very clear about this:
Code:
Server requirements: The following features require to setup subdomain wildcards in your webserver, pointing to your Chevereto installation. Also, you must allow CORS for all your subdomains.
Regardless of the certified status of TMDHosting for Chevereto, this new functionality shouldn't be considered as part of the "certified" label.
In the future, please keep all beta issues on the beta section.