Unable to add ESXi host to Vsphere

Host : 6.0.0 (Build 3620759)

vSphere : 6.0.0 3634794

I have successfully added 2 hosts of the same version no problem.

when I try to add the third host and enter the credentials ( step 2 I think) It returns 'A general error occurred: '

output of vSphere vpxd log ...

2018-01-11T22:07:30.344Z info vpxd[7F6CEF792700] [Originator@6876 sub=Default opID=298b7687-1a9a-4f41-8f1e-20e9b60df1c6-8126-ngc-1c] [VpxLRO] -- ERROR task-internal-62579 -- datacenter-2 -- vim.Datacenter.queryConnectionInfo: vmodl.fault.SystemError:

--> Result:

--> (vmodl.fault.SystemError) {

-->    faultCause = (vmodl.MethodFault) null,

-->    reason = "",

-->    msg = "Received SOAP response fault from [<cs p:00007f6d0d5c0ec0, TCP:192.168.1.193:443>]: queryConnectionInfo

--> A general system error occurred: "

--> }

--> Args:

-->

--> Arg hostname:

--> "192.168.1.193"

--> Arg port:

--> -1

--> Arg username:

--> "root"

--> Arg password:

--> (not shown)

-->

--> Arg sslThumbprint:

-->

I can connect and successfully login to the host and I have checked time and date settings and all seems well.

Any advice would be greatly appreciated as I am at a loss. I have tried the solutions on VMware Knowledge Base but to no avail.

Jason