I was able to get things working by tweaking the registry.
I looked up that "Error 1075" and based on what I found I started to wonder if the service description for
serialosc listed another service that needed to exist/be running before it would start.
regedit I navigated to:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\serialosc - note the "DependsOnService" key? Guessing that "Bonjour Service" was something which no longer exists I figured that might be the problem so I deleted that key.
...the selected "DependsOnService", right-clicked and chose delete.
I then rebooted the machine and serialosc started automatically and monome_sum worked.
I have no idea if this is the correct fix but it works. Maybe @tehn is already aware of this. At a minimum preparing a newer installer which configures things correctly for Window 10 is probably needed.