When creating the account user, did you use an email address that is already being used by a traveler? If so, it may be the failure to save.
The added email needs to be unique, so if it has already been added to another traveler, it will not work. Because the account user email is only used to log in to the CMS, you can create an email address that does not exist (for example,
nomesobrenome@suaagencia.com).