Fun perhaps is the wrong word but while moving isp’s one zoo site refused to load anywhere but on the server.
The others all worked and nmap (my blog) and tools seemed good. After doing a number of workstation things i reset the dns expiry and then it came back like there was no issue with the hsts line (my blog).
I have suspicions but nothing precise to say it was dns zone expiry.
If you read tea leaves leave your thoughts below.