Solving Error 20509 Virtual Machine Manager agent communication is blocked

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During a troubleshoot session on a VMM customer, we noticed that several agents were showing the following error message.

Virtual Machine Manager agent communication is blocked. The version of the VMM agent (x.x.xxxx.x) on the computer server.domain.local is unsupported.


We found out the error message on the agent properties, as shown in the image below.


The root cause of the issue was the customer reinstalled SCVMM 2016 and the RTM version wasn’t recognizing the agent that were installed with a higher version of the product.

The solution was simple, first we found out which version we were running of VMM 2012, and to do that we just need to check on Add/Remove Programs, as depicted on the image below.


Now that we know our current version, we can check this following link which will provide a list of all building numbers for all VMM releases. Let’s get the latest update and apply to the server.


After applying the update to the server (we can do that using Windows Updates, or manually, in the case of the Update Rollup 3, we need to update both: Server and Console).

Note: When performing VMM updates, make sure to create a backup of the VMM Database using VMM console before starting the update process.

After upgrading the VMM, we can check the status of the agent, and the results should be similar to the one listed below:


If the Cumulative Update installed is higher than the initial rollup update, then it is highly recommended to upgrade all agents to the latest version.

Written by Anderson Patricio

Anderson Patricio

Anderson Patricio is a Canadian MVP in Cloud and Datacenter Management, and Office Server and Services, besides the Microsoft Award he also holds a Solutions Master (MCSM) in Exchange and several other certifications. Anderson has been contributing to the Microsoft Community with articles, tutorials, blog posts, twitter, forums and book reviews. He is a regular contributor here at,, and Anderson (Portuguese).

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