Check that the Data Service has been published: In Designer, open the Data Service job and switch to the Endpoint Configuration tab.
In CloverDX Server Console, check Executions history. Find the job and see the log in Log file tab.
Have all required parameters been sent to the server? If there is a required parameter that has not been received, the server returns 500.
Check that the Data Service job is enabled. You can do it in Server on Data Services tab.