Are the players your trying to sell old as this maybe the reason why, most manager dont like buying players 30 or over! if this is the case you will have to sack them!, second you could be on the new tranfer market and so the times your listing them may not be helping! I have found that when I look at the tranfer market late at night/early morning the first ending auction is like 2 or 3 hours away and Im not waiting that long so I just leave! if there are other managers out there with this same opinion then that would certainly explain why you have no bidders.