Hi Srikanth,
Also please check if Manual sample calculation is not selected for your assigned inspection type, in material master -> QM view. If it's not selected, then manual sample calculation is not needed to be done manually as it would be done automatically and plan would be assigned. Only if this is selected, then you need to manually do sample calculation, and only then inspection plan will be assigned.
For rest, follow the steps suggested by Amarnath.
Thanks,
Arijit