After cloning the repository, run a clean build of the application before running it. The settings.xml file in the output directory (probably Mycroft\bin\Debug) needs to have the thumbprint of a certificate that has been installed to the Root Certificate Authority store.

To run the server without TLS, specify --no-tls as a command line argument. To manually specify the certificate to use, use --cert followed by the path to the .pfx file you'd like to use for the server certificate.