I get the below error when I am trying to scan an ESXi server.
Vmware Error FailedToConnect: Value cannot be null. Parameter name: source
Its funny because in past I have managed to connect successfully to the server. SSH is working properly. What is this "source" ? and credentials are not null!
I've seen this error before when the ESXi host did not have a single guest. Does your ESXi host have a guest? Otherwise I'd recommend adding one as a test.