I have two websites on my windows 10 desktop:

• http://www.gregsnativelandscapes.com.au: This one is working fine.
• https://www.gjb.au This one is not working - all I get is 

  This site can’t be reached

  The connection was reset.

What the hell?

I have checked:

•  The bindings - https, correct domain name
• Both web sites are started.
• I have done ISSRESET.
• Checked my A records in Webcentral account.
• I have gone through the IIS settings of each website and checked that they are all the same - they are.

So what else do I need to check?

Is there a specific IIS troubleshooter available that I can download and run?