RC4 has been disabled in .NET applications due to a security vulnerability.
https://technet.microsoft.com/en-us/library/security/2960358.aspx
The best option would be to update your TLS to version 1.1 or 1.2. Alternatively, you can likely reenable RC4 through a registry edit. Firefox/Curl use OpenSSL which does not follow the normal system security policies.
https://technet.microsoft.com/en-us/library/security/2960358.aspx
The best option would be to update your TLS to version 1.1 or 1.2. Alternatively, you can likely reenable RC4 through a registry edit. Firefox/Curl use OpenSSL which does not follow the normal system security policies.