Untrusted connection

Hello, I used Mac os client (v 6.1.3) of SeaFile. Today, I get an alert named “Untrusted connection” (cf. screenshot below). What does that mean ? What I need to do ?

Have a nice day.

If you are using Let’s Encrypt than is your certificate expired. Or you have just bad certificate from untrusted CA or self-signed. This is problem on server not on your PC.