Sigh...I only come back to RDM Mac once in a while because it's so buggy. 184.108.40.206 apparently doesn't respect certs from DigiCert...a major CA. If RDM Mac is using the keychain (as Google Chrome does on the Mac -- and it has no problems with this cert), why doesn't RDM Mac understand it?
Before saying anything, I want to mention I'm no expert in certificate.
That being said, I'm not sure what the issue is.
To display the certificate information, we use a view called SFCertificateView, which should be responsible for the evaluation of the certificate authority. We may be lacking intermediate certificates to accurately evaluate the CA. Or there might me something missing in the data we receive. Or there might be some additional validation that must be done before displaying the certificate.
Regardless, this will requires further investigation.
I'll inform you as soon as we find something.