When trying to install the Universal Update Patch, I get the error, "Game installation not found, please reinstall."

I do have the game installed on another drive, as I use a solid state drive for my operating system, but all my other games patch fine. I even tried putting the update file in the game's install directory, but to no avail. I am enclosing a screenshot.

Contact support. It seems there's something wrong with the patch, as you're not the only one having problems.
See here: http://www.gog.com/forum/aarklash_legacy/aarklash_legacy_has_been_updated_to_version_1134