In February of 2019, we'll be saying goodbye to API 5.1 and any lower versions. We're not doing this to be mean or to make your life harder. API 6.0 is a major improvement over the previous versions with superior security, better API framework, greater stability and more. Here are some important dates to remember:

• April 8, 2018: API 5.1 will be deprecated. PLEASE NOTE: Deprecation does not mean you won't be able to use 5.1. Once deprecated, we will no longer be fixing or making enhancements to API 5.1 (and lower). However, 5.1 (and lower) will continue to work until February 28, 2019.
• February 28, 2019: API endpoints will be shut off.

We're happy to work with you to get you switched over to API 6.0 over the course of the next year. If you need our assistance getting this converted, just reach out and we'll help get you taken care of.

For more information, have a look at our Customer Success Center article on Saying Goodbye to API 5.1.