Some versions of Webuzo make it difficult to change your primary domain (the one used internally and for the Webuzo panels).

Just listing the domains fails, because you can't edit the primary domain information.

Here, I believe for the first time, is the secret:

Both the old and new domains should already exist.

Click on Webuzo > root panel > Users > List Users > Square Pencil Icon (edit) . Changing the user domain changes the old primary domain into a parked domain.