Hi
In network connection drop down see if its blank.If so please select your configured network from the drop down.
of course I checked that. It is a "strange" problem.
Yesterday I renamed the network connection names on vSwitch1 from VM Network to ESX1-Office and ESX2-Office.
Then I migrated the problematic vm back to esx1, changed the nic to connect to ESX1-Office and started the vm. Everything worked fine.
I' migrated it back to esx2 and changed the nic to connect to ESX2-Office network.But still no connection.
It seems that the esx-firewall on esx2 is blocking that nic, but I don't know in the moment how to disable that.