Whenever you have completed with your tests and prepartion and you are ready to take your MicroBiz and Magento instance online, you need to make sure that if you are changing your API APP URL from a development address to a production address that it is changed in the proper settings.  If you do not change this, you will get an error as seen below.

If you navigate in your "Store Operations" tab to the "Linked Apps">"Magento Instance">"Magento API Settings" menu, you will get a screen as shown below.

The highlighted area is where you are going to want to update your URL to whatever new URL you had changed to when switching to production.  Also be sure that if your URL includes a "www." that you include it in the APP API URL.  Without the "www." this error will still occur. After completion, test the connection and see if you are good to go!