If it’s a Program for Cooperative Cataloging (PCC: see field 042) level record input by Library of Congress (DLC in 040), you need OCLC ENHANCE authorization plus PCC member status to make major permanent changes to the record.
See guidelines for enriching PCC records.
If you don't have enhance authorization, send a message including the OCLC number of the record to BibChange@oclc.org with a request to update the record with the corrections that need to be made.
If it is not a PCC record, did you type anything into the 040 tag? If so, delete it and try saving again.
For an example of a PCC record, see record #1076374764. Note DLC in field 040 $a and PCC in field 042 $a.