It is not possible to update WPML when WordPress is not installed in the site’s root. This means that if you set your WordPress site up in a folder like https://mydomain.com/wp/, you will see that the site key is accepted. However, when you try to update your WPML plugin, you’ll see an error message that says that your account is no longer valid.
We are working on a fix for this issue. In the meantime, you can update WPML manually.