The 31-year old had an appeal for his nine-month ban for taking a banned substance rejected, leaving him no closer to knowing his future in the game.
"I am devastated that an honest mistake on my part could cost me my career," Kenny said.
"But I would like to thank Sheffield United, my agent and all my current and former team-mates for their support throughout.
"I am positive I will bounce back and I really hope that this experience will stop others from making the same mistake."
Kenny has been banned for having ephedrine in his system after last season's play-off semi-final against Preston North End but he claims he inadvertently consumed it via tablets he was taking for a chest infection.
But the FA do not see it the same way and it looks as though his nine-month ban will stand.
A statement from the FA said: "The Appeal Board dismissed the appeal by Mr Paddy Kenny against his nine-month suspension for a breach of the FA doping regulations.
"The Regulatory Commission's decision to impose a nine-month suspension was an appropriate measure of the seriousness of the offence."