OC200 uses a self-signed certificate. Seems that it somehow got deleted from the list of trusted certificates on your PC (if it was installed before at all).

Just install the certificate as the message says. Usually it does so automatically if you insist to connect to the OC200 in Chrome.

If this doesn't help, maybe a newer Chrome version refuses to accept the cipher the certificate is using (what should not be dictated by Chrome at all, but Google wants to force people to use strong ciphers and probably latest Chrome doesn't accept TLS 1.2 anymore).

@JSchnee21, the cloud works just as a proxy and uses a certificate from DigiCert Global CA, which is a known CA to your browser.

If you store the self-signed certificate in your trust chain, it becomes known to the browser, too, and the browser will behave as it does with a certificate signed by a known CA such as DigiCert.

doxxie-au wrote

As everyone has said its just a self signed certificate

there is no point installing it in your computer certificate store, as it is issued to localhost, which will never be the name of the device you connect to.

The certificate has been issued for localhost, that's correct.

However, installing the cert in the computer's certificate store allows to connect to the OC200 using its self-signed certificate w/o the annoying security warning of the browser. Whether the Common Name of the certificate is to be matched against the hostname used to access the OC200 can be specified by the trust level for SSL/TLS connections, too:

BTW: In the upcoming Omada SDN Controller you can indeed upload your own self-signed or official certificate to OC200.