I got issue when I checked windows authentication box, same user was able to logon by web client but from vc-client getting issue.
When I typed manually user name and password I was able to logon. I went through logs and got use full KB which is applicable 6.0 also.
2017-11-24T12:55:37.853Z error vpxd[7F3237CF8700] [Originator@6876 sub=GSSAPI opID=F65D9D27-00000004-8a] gss_accept_sec_context failed: (0x00070000, 0x00000000)
2017-11-24T12:55:37.853Z error vpxd[7F3237CF8700] [Originator@6876 sub=GSSAPI opID=F65D9D27-00000004-8a] Supported mechanisms: ({ 1 2 840 113554 1 2 2 }, { 1 3 5 1 5 2 }, { 1 2 840 48018 1 2 2 }, { 1 3 6 1 5 2 5 }, { 1 3 6 1 5 5 2 }, { 1 3 6 1 4 1 311 2 2 10 }, { 1 2 840 113554 1 2 10 })
2017-11-24T12:55:37.861Z info vpxd[7F3237CF8700] [Originator@6876 sub=vpxLro opID=F65D9D27-00000004-8a] [VpxLRO] -- FINISH task-internal-1992
2017-11-24T12:55:37.861Z info vpxd[7F3237CF8700] [Originator@6876 sub=Default opID=F65D9D27-00000004-8a] [VpxLRO] -- ERROR task-internal-1992 -- SessionManager -- vim.SessionManager.loginBySSPI: vim.fault.InvalidLogin:
--> Result:
--> (vim.fault.InvalidLogin) {
--> faultCause = (vmodl.MethodFault) null,
--> msg = ""
--> }
--> Args:
-->
--> Arg base64Token: