I will add the exception, but ...
The Firewall has been OFF since I bought the computer - mainly because I'm configuring it, and it will be used in an observatory, where there will be no data stored on it (or access to the local network).
ALSO, I found - today - that going to skim.com/icam/web using an older Mac (Sys 10.7, I think) gave the same problem - said "connecting", but never connected - even thought I did OK the certificate/JAVA, etc.
Steve