The azeti Site Controller needs a user to connect to the azeti Engine. This user needs special privileges to be able to connect to the broker.
Go to Organization → Users
Click on +Add
Enter Email addres and password
Switch to the Access & Services tab
Click on the Gateway checkbox
Confirm your settings with the Save button
You can always edit the Roles and Services of an user afterwards. A user could also have all privileges, although for security reasons it is recommended creating multiple users depending on they function!