Generated bills approved to send to client go straight to Undoable rather than Bills>Send Bills to Audit Houses

Ledes1998 question: When I generate a bill, print it, and mark it "Approve to Send to Client," it normally goes to Bills>Send Bills to Audit Houses.  I just had one go straight to Undoable.  Help!  Why did it happen and how do I get it to the audit house now?