From our wiki page on our API (http://wiki.x2crm.co...T_API_Reference), this the explanation behind that error code:
Unprocessable entity. This always indicates a data validation error when attempting to set fields of and save an active record model. The client is expected to resolve these issues and resubmit the data with all of the fields formatted in such a way that it is acceptable.
It seems that one or more of the fields you have for the record you are trying to create has data that is not formatted as expected. I would take a look at any custom fields in the admin panel under X2Studio Customization Tools > Manage Fields and make sure that all of the fields for your record have data that conform to the format you specified, assuming you have custom fields for the active record model you are trying to create. If not custom, if you have MySQL access for the app, check the table for the datatypes expected for the fields of that model. Let me know if you have further issues resolving this error code.