First of all, the 4.16 version was built on 4.16.0. Second, I’d delete Plugins\VaRest\Intermediate and Plugins\VaRest\Binaries, then RMB on .uproject and hit “Generate Visual Studio project files”, then open .sln and try to recompile. If that fails, try building using the new method (using FrontEnd) I describe in the documentation for 4.17. I’ll be publishing it in a minute.