Old Post but I had the same issue. We had to install ReqnRoll to replace spekflow and this stopped working for me at one point. I looked everywhere and event reinstalled reqnroll based on recommendations but that still didn't work.

I finally reinstalled: https://dotnet.microsoft.com/en-us/download/dotnet/thank-you/runtime-8.0.14-windows-x64-installer and it started working again.

Hopefully this solution helps someone.