I was having difficulty updating fields in my title block. I would make a change in the sheet set and REGEN but none of the attributes containing fields linked to the sheet set work. I had it working when I first inserted the block. What I found to work is using the UPDATEFIELD command but that was very inefficient.
After revealing my blatant ignorance chasing my tail with this
and that Chris suggested checking FIELDEVAL setting. Thanks Chris, that made things work much better. Now just a simple REGENALL (type REA) updates the fields.
You may also want to check what FIELDEVAL is set to. It sounds like its set to 0 in the drawing.