Your symptoms of "Alexa - unsuccessful" and "Firmware update - stalls" both point at the hub's inability to reach the Internet.
Hubitat doesn't REQUIRE the Internet to function BUT it does use the Internet to get updates, time, and make your dashboards available via the cloud if you allow that. Cloud integrations, such as Alexa of course, need access to that cloud.
You home's LAN/WiFi/ISP configuration will control that, the hub gets no vote.
So - the hub is plugged into a network switch which is certainly live and connected to the internet. My pc is on the same switch. And - this WAS working but stopped. I did get a 500 network error though once. Any ideas of what I need to change or do? The network switch is certainly live and active I just plugged a laptop into that same port and no problems with it. Is there a place I can log a trouble ticket with Hubitat other than posting here?
Yes - I immediately set it BACK to a fixed IP. It is all working now I don't know enough about HE to know exactly what did it but it would not go until I did the network reset - then back to DHCP ... I did a firmware update with DHCP it worked. Then switched to static IP again - and the problems I was having getting Alexa installed ALSO then worked.