OK Guys, elsewhere I saw a note that the sig now has to be 'pure' html, instead of MLS codes with '[' brackets.
So I went back to the archives, found a post with my old sig block and did a 'view source' (right click to find it, or it is on the view menu.) That opens a Notepad window with the html - use ctrl-F to 'find' your post (find your name?) and then identify which bit of html is your sig block. Highlight it and cut-and-paste it to the sig area in 'my profile'.