timeout issue possibly relating to proxy

When I run:
$ cs foundweekends/giter8

I get (after a minute or so):
An unexpected error occurred: Please check your internet connection.
Exception message: connection timed out: api.github.com/192.30.253.116:443 to https://api.github.com/repos/foundweekends/giter8/git/refs/heads/master

Internet connection is OK (can access that from other tools, e.g. curl)

have set proxy using JAVA_OPTS eg:

$ echo $JAVA_OPTS
-Dhttp.proxyHost=my.proxy.server -Dhttp.proxyPort=1234 -Dhttps.proxyHost=my.proxy.server -Dhttps.proxyPort=1234

plus everything else on my system seems happy proxy wise

I am on centos 7.3
Java 1.8