Lansweeper tech support responded to me and suggested the following.
- Restart both the Lansweeper server and web server (IIS Express or World Wide Web Publishing) service under services.msc on your Lansweeper server and verify if the deployments work and the installer logs populate.
- You're running a bit of an older Lansweeper version atm, we do recommend updating to our latest release by going through the following guide: https://www.lansweeper.com/knowledgebase/updating-your-installation/
- Try to deploy a package through Deployment \ Installer Packages and see if the Installer logs log this new deployment action.
First, I re-booted the PC Lansweeper is running on. After that the "Cmd - Mass Messenger" ran successfully. I did update Lansweeper after that but it was the reboot that got things working. No idea why.
Since then I've developed a number of deployment packages for software upgrades. It's takes a good bit of trial and error but it starts to make sense after a while.
Good luck.