Thanks Colin. Actually, I did figure it out later. Those dropdowns actually aren't intended to match field names in your remote database. It's an unintuitive system (kind of convoluted, really), but what fixed it for me was that in Remote Enrolment Sync section, I had to enter the field name of the remote db that contained usernames. Then in the Field Mapping section, I also selected the local field `username` . I guess I had tried a bunch of combinations through trial and error but hadn't gotten that part quite right. Once I did, it all came together. It's working!
Thanks,
Scot