I ran into a issue where I couldn’t migration a powered on machine between to Hyper-V hosts without shared storage.
The error was Element Not Found. (0x80070490)
Destination host rejected the request
After digging around the only hint in the event log was the above , Virtual Machine Management Service blocked a connection request Event 20400
I then changed the network to use the dedicated ip address on both hosts istead of “use any available network for live migration”
Honestly not sure why I could ping on ipv6 , I suspect a 3rd party firewall but ran out of time to trouble shoot