I'm trying to LUM enable a user via iManager 2.7.3 on OES2

I get a -609 error for any user, including a brand new user I've created. All accounts have a uniqueID.

Looking at an eDirectory trace, the -609 error is thrown when an attempt to add the posixAccount AuxClass is made, so I assume one of the mandatory attributes of that class is missing.. but no idea which one!