Error: CMN.ATO.GEN.438065 - Declaration signatory identifier is required.

Solution:

Select "Gear wheel" (Business/Agent's Settings) > "Profile"


Press "Settings" > "Contact Details"

Ensure you are the signatory. If your name is not there in the signatory field, (Make sure you've added yourself as a "client" so it will sync/inject your details as "Primary Contact/Signatory)