Just had a user tell me that her sign-off wasn't appearing on formletters, hadn't done for months apparently (why did it take her so long to tell me...?). Anyhoo, found that the If Statement based on her OPID code had an extra space after the field name, and this stopped it from working. Just thought I'd share in case anybody ever gets a similar issue.
So where text says IF "<AGCY.SYSTEMENV.OPID>"=AB, etc, and there is a space between > and ", the If Statement doesn't work. But I suppose you all know that already.... :)