Yadagiri,
It means exactly what it says. The product mentioned does not exist in APO. You can verify by going into APO and reviewing in /SAPAPO/MAT1.
Clear all blocked queues. SMQ1/SMQ2.
Create an integration model for the material/plant in ECC. CFM1. Activate the newly created Integration model in ECC. CFM2.
Best Regards,
DB49