Point 1- You can not create Requisition (PR) w.r.t to RFQ
Point 2- You can check that document type mapping is complete for RFQ document type
this can found in Materials Management-->Purchasing-> Purchase Orders-->Define Document type -->Allowed Item categories --see your PR document type available there or not-- Same RFQ is also mapped to PR -- there is no link between RFQ and PO document types
point 3- RFQ is normally created from PR. Quantities can be reduced in PR but not in RFQ. If your RFQ is created from PR.
In order system does not exceed the PR quantity requested - do the following as well
IMG>>Material Management>>Purchasing>>Environment Data>>Define Attributes of system Messagae>>System Messages>>
Maintain Version 00 Application -06- Message No 076 Materials of requisition & item & alr. ordered in full as Eror message
You have to insert new entry