Error:An unknown error occurred while invoking the service metadata component. Failed to generate service reference

As a temporary solution to this issue I have added a new Project to my solution, set it to Asp Core 1.1 and added the connected service that way which appears to work.

It would seem 2.1 is broken currently and I'll have to wait for updates before doing it directly in my Project.

Edit: Thanks to User3130628. This has now been fixed and appears to be working, even in VS 15.7.5.

I suspect the Core framework has been updated and this has corrected the issue.

Till 2018-07-31, it still has problems for NET Core 2.1.x to add a service reference for WCF in VS2017 (v15.7.5). You can create Net 2.0.x project to create the connected service, it'll work perfect. Then copy the 'Connected Services' sub-directory in project to new NET core v2.1.x project.

Installs the following packages via NuGet such as this image:

NuGet Packages for Connected Services

Compiled successfully in NET Core 2.1.x project.

As of today VS2017 15.8.1 it seems to be working again with .Net core 2.1.401