If the WPML is not registered properly on that site then please try to follow the below steps:
1. Login to your WPML.org account >> Go to the Sites page: https://wpml.org/account/sites/
2. Delete the existing site key(if it exists).
3. Login to your site and go to the Dashboard >> Plugins >> Add new > Commercial tab and click the Unregister WPML from this site link if that link exists.
4. Then click the Register WPML link.
5. Click the Get a key for this site link.
6 It will generate the Key for your site and you can also assign the credits using that popup.
7. Copy the key, and paste it back into the input box, and press the Register button.
Please let me know if this resolves the issue or if you need further assistance with this issue.