Microsoft Service Configuration Editor - Could Not Load File Or Assembly

I'm getting stumped by a very basic error. I'm trying to add endpoints to a service through the WCF Service Configuration Editor, and it can't find the default output. Here's every step I can take to reproduce the error.

Add New WCF Service Application

Build Solution

Edit WCF Configuration

Create New Service

Browse to Project Directory for Service Type

Error Message

This should work, but instead I get the following error message:

Could not load file or assembly
'file://...\emptyservice\bin\EmptyService.dll'
or one of its dependencies.
Operation is not supported.
(Exception from HRESULT: 0x80131515)

What am I doing wrong?

Make sure you open the 'EmptyService.dll' library in your 'bin\Debug' folder.

I had the '... Operation is not supported. (Exception from HRESULT: 0x80131515)' message when trying to open the library in the 'publish' folder. I published my service from within Visual Studio using the 'Publish Web Site' option.