Hi Ravindran,
Please check if the factory calendar being used in APO is in sync with ECC - You can have a look at below document on how to update factory calendar in APO -
Automation of Factory Calendar Update Between ECC and APO via Process Chain/Batch Jobs
Also running RIMODINI on the work center IM also sometimes helps in sending the updated capacity to APO.
Please check if it helps.
Regards,
Alok