Why is the thumbprint my Tentacle sees different than my Server thumbprint?

In my Tentacle logs, I see the message

The remote machine was expected to supply a certificate with thumbprint: 0750EB3BC9857C3E5BE38A103208284265618112; instead the machine provided: B34461DE97FE3B758481D393B70481F704EEA355

What could be causing this?

This can be caused by what is know as a Man In The Middle (MITM) issue. This is when a piece of networking equipment, like a proxy server, intercepts the request and inserts its own certificate instead of the original.

The recommended method to resolve this issue is to work with your networking team and remove the MITM certificate replacement for Octopus Deploy Tentacles.

As a last resort, you could use the update-trust Tentacle command to change the trusted thumbprint from the Octopus Deploy to that of the Proxy server.