So I have en older Tea Commerce on an Umbraco 6, and QuickPay just changed so they don't support TLS1.0 ... Breaking our Tea Commerce... Found a fix I just wanted to post here if anyone else gets into trouble...:

Installed WebActivatorEx and then:

Created an AssemblyInfo.cs:

using WebActivatorEx;
using MyNamespace;

[assembly: PostApplicationStartMethod(typeof(Init), "Run")]

Created an Init Class:

using System.Net;

namespace MyNamespace
{
    public static class Init
    {
        public static void Run()
        {
            ServicePointManager.SecurityProtocol = (SecurityProtocolType)192 | (SecurityProtocolType)768 | (SecurityProtocolType)3072;
        }
    }
}