[Resolved] Unable to set up different domains per language

Problem:
The client is trying to set up Spanish and Dutch translations for their website using separate domains, but the domains are being marked as 'not valid' despite being set up as aliases and not redirects.

Solution:
1. We suggested that the error might be a false positive and recommended saving the settings without the validation option and then visiting the translation to see if it works.
2. We advised the client to check their

wp-config.php

file for entries that define home and site URLs dynamically, which could cause false positives, and to comment them out if present.
3. We identified that the issue might be related to DNS setup or specific settings with the client's web host, One.com, and recommended contacting their support for assistance.
4. We also suggested adding the .es domain to the DNS settings of the .nl domain, as it was not included in the screenshots provided by the client.
5. After testing the client's site on a virtual server, we confirmed that there were no issues with the theme or plugins, and reiterated the need for the client to contact their hosting support and domain providers for help with DNS settings.

If the solution provided here is not relevant to your case, either because it's outdated or not applicable, we highly recommend checking related known issues, verifying the version of the permanent fix, and confirming that you have installed the latest versions of themes and plugins. If you still need assistance, please open a new support ticket.