I recently converted an AT&T Access (no AF) card to DoubleCash, and the materials I got seemed to say that you have to have a minimum of $25 cashback to do a conversion from cashback to TYP.
So I wonder if the $10 cashback to TYP conversions are failing because they under that limit, but Citi's website is too broken to block you from redeeming too little or tell you that's the problem?