Achei isso:
"Registering the first user
After installing the server, open a browser to the domain you used (or #^http://localhost:8000 for local installs). You should be redirected to the login screen. Click the link to register a new user instead, and complete the registration.
The first user registration will always be permitted, but subsequent registrations will require an invite link which includes a code. You can invite additional users by clicking on your username in the top left, then selecting “Invite users”.
(#^https://www.focalboard.com/guide/server-setup)
Isso explica porque ontem consegui criar minha conta e hoje não...
A questão é: por quê, Santo Deus? E se eu quisesse abrir para o público? #focalboard

