The forum is configured such that users cannot create an account - only attend via invitation.
(apologies, I can’t find the setting to provide the exact title)
The default message seems to be hard coded:
“An account is required. Please ask an existing member for an invite or log in to continue.”
Two Things Of Note re:
it’s set to the standard message instructing create an account or login.
editing it has no effect on the alternative message instructing them to ask for an invite or login
(even after a restart of the browser)
(and I was unable to find an alternative field to edit instead)