Create a credit note

In AX2009 we are unable to "mark"  either an entire invoice or line item under AR>Sales Order detail>Functions>create credit note on orders with the invoiced status-this was tried under Admin so not a security issue and we still have the same results.  We are able to "mark" orders or lines that are not in Invoiced status.  I am looking at this to credit shortages or returns, etc.