Well, embarrassing, but perhaps it will save someone some time.
Short answer, nlog.config file is in the wrong directory.
The solution has two projects, the service host/installer project and a project where the logic/work is done. Service installs from the debug folder for the service host/installer (still in early testing). The logic dll, is loaded from the logic project debug folder by the service hsot. The logic folder contains the nlog.config. So when the service starts the nlog.config file can't be found where the service host is running.
The service host has no reference to the service.dll, not a problem as the dll is loaded at run time, but the nlog.config file was an issue.
The simple solution for creating the service is to change the logic/work project output to be the same as the service host output directory.