Reasons for not up dating the planned revenue in internal order

Dear CO experts

What are the probable reasons for not up dating the the planned revenue in internal order . Eg : The order value in CRM order is not flowing to the planned revenue in internal order . The GL has been defined for the same in ECC and CRM .

What are the points to be checked if the planned revenue does not update the internal order.

Where can i find the documentation for the settings of CRM to ECC controlling.

Regards

Raj