Hi DanielMarshall,
Thanks for reaching out. Last week we made a change to our API meaning we will no longer accept connections using TLS1.0. As Triboss has said, you will need to update the SDK and ensure you are using TLS1.1 or greater.
Here is a link to our blog post which has more information on this - http://myobapi.tumblr.com/post/177017431449/tls10-no-longer-supported
Thanks,
Jacob
MYOB API Team
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