Reported by @Bishbulb
"In my case the ServiceControl.Contracts.dll/pdb files were not present in that directory. I had to do a full uninstall/reinstall of ServiceControl in order to get things working.
I had previously upgraded from SC 1.2.0 to 1.3.0 by using Chocolatey cup ServiceControl.install which appears to have left things in a bad state. I used Chocolatey to upgrade SC to 1.3.0 on three different machines and each one had this same problem.
What ended up working for me was to uninstall SC (choco uninstall ServiceControl.install) and then reinstall (choco install ServiceControl.install)."
Full discussion: #372 (comment)