Error while activating IM in CFM2

Dear Friends,

I would like to have a solution to the folowing problem.

I've tried to activate integration models in ECC with transaction CFM2.

I've build several integration models for class, customer, masterdata and transaction data.

When I try to activate one of these integration models the system gives the next error message:

inbound queue blocked

Function/Q/SAPAPO/CIF_CBASE_INB

Text: Reference product has not been classified

This error is only coming for configarable material, for non configurable material I am not getting this error.

Is there any setting?

I would like to know what causes the problem and how to solve this problem.

I hope to receive an answer soon.

Thanks for the help!

kind regards,