Result: built test is not shown in the Test
Visual Studio can change the default processor architecture when it loads. While looking endlessly trying to figure out the issue, I finally figured it out, that it wasn't really Specflow causing the issue.
If you have references that require a special architecture, it will prevent the tests from showing up in the test explorer. Change the architecture to x86 or x64 based on your needs.
Another thing you can do to see the build issues is open the Output window and change the dropdown to Tests during build. It will highlight any information of things taking place during your build.
I felt somebody should mention it just in case.