The knowledge base article Reecardo was thinking about is for the Get All Locations piece of SD.DataServices. I'm not aware of an article for this model.
What I would recommend is to open SD.DataServices inside Designer & then launch the 'Get Location for User' model. You will need to provide an e-mail address or user id. Then see if the model completes successfully or fails. I would recommend trying it once with an e-mail address & once with the userid as the model has two paths depending on the information provided.
Once we know exactly where the model is failing we should be able to provide an answer in how to fix the issue.