I 'm new to cockpit and had connection problem

I have here to desktop pc’s with linux mint
On both i installed cockpit.
I use the last version of firefiox
But when i try to add the a new host i’ve got the message Cockpit could not contact the specified host.
But when type as address for the other Linux machine.
the i’ve got this error

when i click on the button accept the risk and move on
Then i see the login screen of the other host. Why can i add the other host when i’m loged in to the following adress localhost:9090 in firefox on linux mint

This is not an issue about Cockpit CMS. You have to do some research about (self signed) ssl certificates - or just don’t use https on your local development machine. should work without the error message.