[Resolved] Activation on subdomain

Problem:
You are trying to activate the WPML plugin on your subdomain but encountering errors such as 'Your account allows you to build only 3 "production" sites with WPML,' and 'Unable to register: Site key not matching' when using the parent website key.
Solution:
If you are using a Multisite Setup, you should first register your main site so that the same site key will apply to all subsites. For detailed instructions on how to register WPML on a Multisite Setup, please visit https://wpml.org/documentation/support/multisite-support/#install-wpml-multisite.
If your subdomains are separate WordPress installations and not part of a Multisite setup, you will need to register each one individually and create a separate site key for each URL.

Please note that this solution might be irrelevant if it's outdated or not applicable to your case. 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 you still need assistance, please open a new support ticket at WPML support forum.