I couldn't do online check-in nor use the self-service check-in kiosks at the airports, even though I'm ExecPlat. I asked the personnel at the Admiral's club and they said it could happen if my name is similar to a name on the no-fly list, which would require the ticket agent to ask for my ID before checking me in.

I was told that you can change the name that appears on your ticket (e.g. add/remove your middle initial or mother's maiden name). This strategy didn't work for me. But after a year of pain, it finally went away and now I can check in online

Good Luck