arturM-15

Problem:
You are using WPML to manage translations for your website with separate domains for different languages. The language switcher works on the .pl domain but not on the .com domain. Additionally, saving settings in WPML->Languages results in a red void/invalid message on the .com domain.
Solution:
First, ensure that all your domains (or subdomains) point to the same WordPress site where WPML is installed. For more information, please visit this documentation.
Next, deactivate the "Validate on save" option, enter your second domain, save your changes, and then test the domain to see if it works. The validation message might be a false positive. After translating the page, check if you can access it using your secondary domain. If it doesn't work, your second domain might not be configured correctly.
Additionally, check your config.php file for these lines:

Commenting out these lines can resolve the issue with the language switcher.

If this solution does not apply to your case, or if it seems outdated, we highly recommend checking related known issues at https://wpml.org/known-issues/, verifying the version of the permanent fix, and confirming that you have installed the latest versions of themes and plugins. If issues persist, please open a new support ticket at WPML support forum.