IIS on Windows 10 no longer serving my websites

My websites were working, i.e. I could access them on my mobile phone.

But something has happened abd they are not longer accessible - "NOT FOUND"

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.

So what else do I need to check?

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