MES Start Activity Rest

I am trying to start activity in MES via web page using REST Api.
I have traced all the methods, but cannot get some of them to work.
Fist one is start activity, which works fine. After that is DefaultJobNum in LaborSvc which is just cannot get to work.
My input parameter is job number, and ds but it comes back with 500 code.

And in the even viewer i get below

Business Logic Error
Business Layer Exception
BLException
Description: Labor has not changed.
Program: Erp.Services.BO.Labor.dll
Method: DefaultJobNum
Line Number: 4980
Column Number: 17
Table: LaborDtl
Server Trace Stack: at Erp.Services.BO.LaborSvc.DefaultJobNum(LaborTableset& ds, String jobNum) in C:_Releases\ERP\UD10.1.600.9\Source\Server\Services\BO\Labor\Labor.cs:line 4980

I am not sure what i am doing wrong

You need to send a RowMod looks like to the LaborHead DataSet

Thanks, that worked. Do i have to pass anything else inside ds{}?
Thanks

@anyac I’m trying to use the startactivity endpoint to push the transaction details to Epicor. It runs fine but nothing appears in timeandexpense entry screen for that user. Could you please share the json structure and sequence of SVCs that worked for you to store data in Epicor??