This is an FYI if you find that payments now fail against the sandbox as of the 13th Dec 2016.

This is what BrainTree have done:

We want to make sure you're aware that Braintree will stop accepting connections encrypted using TLS 1.0 beginning January 31, 2017. Following the PCI DSS 3.1 requirements, all requests must use TLS 1.2+. Learn how to ensure you're using TLS 1.2.

We will be transitioning the sandbox to TLS 1.2 on December 13th, allowing you plenty of time to test before we make the changes to production. After December 13th, sandbox will no longer support TLS versions older than 1.2. We expect significant impact to Java environments, including Android. Other environments, including .NET, PHP, Ruby, Python and Node.js, may also be affected. For complete details, see the Braintree documentation on Github.

As Merchello 2.3.2 uses an older version of BrainTree SDK that does not support TLS 1.2+, sandbox payments now fail and production ones will start failing on the 31st Jan.

You can get updates on the issue here http://issues.merchello.com/youtrack/issue/M-1221

If you need to get a working BrainTree to the sandbox before then, download the Merchello source code, target each project to .NET 4.5.2 (up from 4.5) and use Nuget to upgrade the BrainTree SDK to version 3.3.0.

Compile and copy over the Merchello dlls and the new Braintree.dll (and remove the old one from the bin directory).