Second domain name pointing to NCP - authenticate

I have pointed an additional domain name to my NCP.
It works.
But unlike my original domain - the second domain gives warning on the browser that the site is not safe.
How do I give the second domain accreditation??

Can use nc-trusted-domains to add it
either from terminal/ssh useing ncp-config or thru ncp-web
and letsencryp to get another certificate.

Hi @OliverV
Thank you
I have added it in the nc-trusted domain
having clicked the apply - the dot next to the apply button is red
and the message in the text box below says this
[ nc-trusted-domains ] (Wed Jan 20 15:32:14 GMT 2021)
System config value trusted_domains => 20 set to string

and when I am connecting from a fresh browser a message still comes up saying unsafe attackers may still you etc.
What am I doing wrong?