This integration relies on the OCLC number matching to populate the call numbers. For the call number to be filled correctly, both the incoming request and the record in your OPAC need to contain an OCLC number. Without one or the other, the call number cannot be filled in.
Check the request and the record in your OPAC to ensure both of these conditions are met.
If you have a request that did not populate the call number, despite the OCLC number present in the OPAC and request, please contact OCLC Support with your OCLC Symbol, the ILL request ID, and the OCLC number of the title.