Thank you for your post!
The first issue (when trying to open the file locatlly) I believe you are getting the message below. If you check that box and select "Use Local Version" it will leave you alone until it is hosted again.
The connection failed issue is usually caused by a communication problem on Port 443 to the Server Machine. You might do a port scan from the client to the host to see if it is open. If you have any firewalls on the server you might temporarily turn it off to see if that is the cause. You might need to make exceptions for Port 443 on the Firewall or any security software.
I hope this helps!