Error: The system cannot find the specified file, ClassID: {F94EEEBC-9966-4B32-9C9C-763B22E31B20}
looks like C:\Program Files (x86)\RemObjects Software\RemObjects SDK (Common)\Bin\RemObjects.SDK.CodeGen4.dll wasn’t registered correctly by some reasons.
Gacutil is a part of Microsoft Windows SDK and can be found at C:\Program Files (x86)\Microsoft SDKs\Windows\v10.0A\bin\NETFX 4.8.1 Tools or similar folder
The problem may be due to the fact that the RemObject libraries are not installed on C:.
gacutil was installed but not in Path.
After executing the .cmd file there were new errors, but I first uninstalled all RO libraries and then reinstalled the SDK on C:.
FirstSampleServer is now compiling without errors.
With the DLL server (code first), however, the interface unit is still not generated, but with the RODL version it is. I will test this further, the DLL server could be important for the current project.
in your case (Code-First DLL server), I can suggest to create additional project that uses http server and your _Impl(s) so you can receive .RODL from Code-First Server and generate _Intf for client-side.