This thread is resolved. Here is a description of the problem and solution.
Problem: Can't install WPML updates after host change ("undefined" is the error I see when I try to update).
Solution: Client confirmed that re-registering the website solved the issue.
What you would need to do is go to your WordPress backend > Plugins > Add new > Commercial > Unregister WPML and register it again with a newly generated key (you can delete the existing one and create a new one) from your WPML.org account (https://wpml.org/account/sites/).
Relevant Documentation: https://wpml.org/faq/install-wpml/#register
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