After upgrading VMorkstation to version 16 Pro it can't connect to an ESXi server anymore

[GMGallo]

Hi, I have an ESXi server running on the local network.  I recently upgraded my VMware Workstation to  version 16.1.2 build-17966106.

After the upgrade It can't log in to the server I've been using for years.

After entering the correct admin credentials I get the following error:

Failed to connect to (server IP address). A secure connection to the server could not be established.

PING confirms that the server is reachable. Is this a security certificate missing or something else?

[wila]

What version ESXi server are you running?

FWIW, to me it sounds like that your ESXi server is running with an old SSL/TLS stack which is no longer allowed by the latest VMware Workstation version.

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Wil

[GMGallo]

I'm running ESXi  version 7.0.0 since January of this year which was running fine.

The server doesn't allow me to log in to its web console with FireFox either in this computer (windows 10, 64bit)

I have other computer in the same LAN also Windows 10, 64bit running Workstation 15 which has no problem connecting to the server as usual, or by browser to its web console.

It seems that you are on the right track, but what could have changed on the first computer after the upgrade to V16?

[wila]

Hm.. I was hoping you would come up with a much older version of ESXi...

The documentation on ESXi's TLS settings is here:
https://docs.vmware.com/en/VMware-vSphere/7.0/com.vmware.vsphere.security.doc/GUID-BDCE47DD-8AD2-4C9...

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Wil

[GMGallo · Accepted solution]

I found the problem. First I made sure that TSL 1.1 and 1.2 were enabled on my computer, which they did. But before I commit to mess with the ESXi TSL configuration. I googled the error code reported by Firefox: PR_END_OF_FILE_ERROR.  From there I got some clues of what could be interfering with the secure connection.

The culprit was the VPN software which I had running on the problem computer. turning it off the problem went away. For additional confidence I also added the server's IP address to the list of exceptions in my antivirus real time web protection. Actually, it is the only thing in that list.

Hope this will help others with similar problems to look for unexpected side effects of VPNs or antivirus.