After some troubleshooting it appears that Fusion 12 deletes the Mac OS X default route!
Sometimes it is the IPv4 default route and others it is the IPv6 default route...
It happens every time you have a VM that is configured with NAT.
You do not even have to start one of those VM... just start fusion, if you have one VM with NAT enabled in your VM list, then the Mac OS default route is removed and your internet connection on your Mac is cut.
The solution is to convert all VM to Bridge - AUTO DETECT
Over bridge mode doesn't seem to work for me (i.e.: Bridge - WIFI)
And I mean ALL VM, because if you leave one VM with NAT in your VM list (not sure if it has to be in "pause" state, I stopped troubleshooting after I found my solution)
How is this possible? Looks like a beta software!
What is infuriating for me is that I bought Fusion 12 (as an upgrade) only a few months ago... but it is not possible to raise a support ticket (I do not seem to have a valid product that qualifies).
I understand software have bugs, but do not make it hard to raise support ticket and force your paying customers the route of community forums (as great as they are).
So basically, I have now a working a solution... not ideal as I sometimes used NAT to leverage some native VPN, at least I can use my VM again... but I am left very disappointed with this experience!
Now... why did I switch from Parallels to VMware all of those years ago again?
hum... next renewal might be time to reconsider that move...