Post Upgrading your ESXi Host or While trying to add a New ESXi Host to the vCenter Server you might get the below Error:

“Host Not Responding” or “Timed out waiting for vpxa to start”

In My Scenario ESXi Host was in Not Responding State.

While Reviewing the logs I saw the below Errors:

VPXA Logs:

Location: /Var/Logs/VPXA.log

2020-06-27T01:30:34.593Z warning vpxa[7616B70] [Originator@6876 sub=hostdstats] [FetchQuickStats] GetTranslators -- host to vpxd translation is empty. Dropping results
2020-06-27T01:30:34.593Z info vpxa[7616B70] [Originator@6876 sub=hostdstats] [PollCurrentStats] Failed to gather host quickStats from provided host metrics.
2020-06-27T01:30:34.666Z verbose vpxa[7679B70] [Originator@6876 sub=vpxaInvtHost] [VpxaInvtHost] Increment master gen. no to (110): Event:VpxaHalEvent::CheckQueuedEvents
2020-06-27T01:30:38.579Z verbose vpxa[74D3B70] [Originator@6876 sub=SoapAdapter] Responded to service state request
2020-06-27T01:30:38.618Z warning vpxa[7616B70] [Originator@6876 sub=SoapAdapter] Unsupported version URI "urn:vpxa3/6.0"
2020-06-27T01:30:38.618Z error vpxa[7616B70] [Originator@6876 sub=SoapAdapter] Unsupported version URI "urn:vpxa3/6.0"
-->
--> while parsing SOAP body
--> at line 9, column 0
-->
--> while parsing SOAP envelope
--> at line 2, column 0
-->
--> while parsing HTTP request before method was determined
--> at line 1, column 0

This Error seems to be with talking about Unsupported Version URI.

This happens when generally when there is either an Unsupported Scenario or vCenter is trying to communicate with the ESXi Host using an Unsupported API Call.

Let’s take these two scenarios separately:

Scenario 1: ESXi Host in Not Responding State Post Upgrade:

In This scenario you just need to follow the below steps to request vCenter to Reestablish the connection with the Upgraded ESXi Host.

Run the Below Commands to Refresh the ESXi Management Agents:

[root@nj51esx:~] /etc/init.d/hostd Stop
[root@nj51esx:~] /etc/init.d/vpxa Stop

[root@nj51esx:~] /etc/init.d/hostd Start
[root@nj51esx:~] /etc/init.d/vpxa Start

Post this you can go ahead and Connect the ESXi Host back to the vCenter Server.

Steps:

• Right Click on the ESXi Host showing as Not Responding.
• Select Connection and Click Connect.

Scenario 2: Unable to add ESXi Host to the vCenter Server.

In this scenario you need to understand that VPXA is unable to connect to VPXD and its failing with the Error: Unsupported version URI. So there is a Version Mismatch between the vCenter Server and the ESXi Host

So confirm the below two Things from Both vCenter Server and ESXi Server.

ESXi Server: Check the Build Version of ESXi Host.

You can check this by Running the Command

[root@nj51esxp:~] esxcli system version get
   Product: VMware ESXi
   Version: 6.5.0
   Build: Releasebuild-9298722
   Update: 2
   Patch: 57

vCenter Server:

You can check the vCenter Version from the Information below:

Once you have the Build Version of Both the ESXi Host and vCenter Version. You can match them with the Exact Version using the Articles Below:

Build numbers and versions of VMware vCenter Server

Build numbers and versions of VMware ESXi/ESX

You can now check if your ESXi Version is supported with the vCenter Version using the Link Below:

VMware Product Interoperability Matrices