I ran into a tentacle upgrade issue which turned out to be related to uninstalling the previous version of the tentacle. Essentially, the old tentacle couldn’t be uninstalled - when I manually tried it, it complained of missing installation media with a path to the upgrade location with the Octopus home directory (which Octopus wipes out after a successful upgrade). I’m sure this isn’t related in any way to your installer – most likely something borked the Windows Installer cache and caused the problem. Regardless, I was unable to use the correct version of the tentacle downloaded from the Octopus website to fix the problem: the uninstaller complained that the downloaded MSI wasn’t valid for the product. I was able to find a copy of the bundled installer that Octopus used to upgrade the tentacle on another box (which had a failed install attempt in the past) and grab the Octopus.Tentacle-x64.msi from there and put it into the path the uninstaller was looking for the file in. This allowed the upgrade task to complete.
My questions are: is there a difference between, say, the downloadable Octopus.Tentacle.3.16.2-x64.msi and the Octopus.Tentacle-x64 file (which also contains the version 3.16.2 tentacle) that was bundled with Octopus Server 4.0.10? There’s definitely some difference besides the filename since their file hashes aren’t identical. If so, is there a handy place to get that bundled MSI from your site? Because, if I hadn’t just happened to have a copy of the bundled tentacle installer lying on another server, I wouldn’t have been able to cleanly uninstall/upgrade the tentacle.