Cannot Create order


I am new to Sage. I am making orders on Sage300 using REST Api. I have created customer on Sage using the API successfully

I am using C# for integration

I am unable to create order on Sage. The API returns Internal Server Error. I have check credentials and rights also and i did not find any issue with them. I also inserted values directly into Order header and order line details tables, they were successfully inserted but when I tried to find order from Sage it was not found.

Kindly let me know what could be the issue.