Caddy needs administrator access to install certificates. You’ll need to run it with elevated privileges to install the certs.
But it’s complicated, because you need to make sure that the right storage location is used when installing the CA certs – when running as a privileged user, the caddy trust command might try to use the wrong storage location.
We have some improvements planned to make this smoother:
For now, you’ll probably be better off installing the root cert manually (find guides on Google for instructions on adding certificates to your system and/or browser trust stores). You can find the root cert in Caddy’s storage, under pki/authorities/local/root.crt.