This post is likely to be updated as I find issues.
I built up a process to do it at work, and on most systems it worked fine. On some systems it didn't. I had very little logs or events to troubleshoot it with. I was getting on the host a blank Sysmon log. The only linking factor was they were all windows servers.
Nothing Logged in Sysmon logs.
Doing some standard troubleshooting, uninstall, reboot, reinstall, reboot. No go.Then I noticed the directory we'd deployed it to was were the sysmon service was pointing. Seems our install script set it to run from there.
I uninstalled and moved the exe to a different directory and it worked. Sysmon extracts a .sys driver file, that was unfortunately being overwritten by our deployment software, and not loading the driver, hence no logs. Hope this helps someone else.