Hi Amit
There might lot of reasons for this issue. We could check one by one
1. Check if your DSO request is activated and there are records added
2. Check if you have filters set up in the DTP from DSO to Cube
3. Check if you have any start routine to delete certain data. For instance, Delete source if material type is 'blank'. If the data in DSO has blank material type, it will get deleted there
Please share these details. The we could get in further