Having difficulties install this starter kit

[adambant]

Hello,

When I attempt to install this starterkit I get the following error.
configuring pattern lab...
downloading the starterkit. this may take a few minutes...
the starterkit wasn't downloaded because:

file_get_contents(https://github.com/pattern-lab/starterkit-mustache-demo/archive/master.tar.gz): failed to open stream: Connection refused

Running composer diagnose yields this:
composer diagnose
Checking composer.json: OK
Checking platform settings: OK
Checking git settings: OK
Checking http connectivity to packagist: Warning: Accessing packagist.org over http which is an insecure protocol. OK
Checking https connectivity to packagist: OK
Checking HTTP proxy: OK
Checking HTTP proxy support for request_fulluri: OK
Checking HTTPS proxy support for request_fulluri: OK
Checking github.com rate limit: OK
Checking disk free space: OK

But I can manually download the https://github.com/pattern-lab/starterkit-mustache-demo/archive/master.tar.gz file using curl and wget.

[adambant]

I will add I am behind a corporate proxy server, but have all other services configured for this. As the composer diagnose shows.