Hello @christian,
I appreciate that you guys are constantly supporting your findings with an article to further help my understanding. The hosting service provider is complaining that there is a syntax error in the theme and there it is not their responsibility.
I have a subdomain with an identical site and it works. I also downloaded the non-working site onto my computer and it also works. So I am suspecting it has something to do with the primary domain. As you know, each domain/sub-domain has its own PHP configuration. I am comparing the settings on the sub-domain against the main domain.
As to your network suspicion, I have also tried accessing the site from several locations via VPN. None of them work. Please do share if you have other thoughts.
If all fails, I am going to move to another web hosting provider.