The same happened to my AA-Plat account last year. One rep explained that the account was marked as not eligible for retention offers. So after many tries I gave up and cancelled. I think the selection is random, and does happen periodically. Maybe the following is worth testing in such a case: connecting to retentions from another Citi account that you may want to close. After discussing the other account with a specialist, you can inquire about your AA-Plat as well.