The rocker is one of the star judges on the Tv talent show alongside will.i.am, Sir Tom Jones and Jessie J, and was set to shoot a Tv commercial for the upcoming second season, which is set to kick off next month (Mar13).
However, the Irish star has caught a bug and his doctor advised him to rest - forcing him to miss out on the promo.
A source tells Britain's The Sun, "The coaches have all been working really hard on the new series in order to make it better than last year. Danny also has commitments with his band but it has obviously all got too much and he has been struck down by a nasty bug.
"Doctors have advised him to rest and he doesn't know when he'll be able to return to filming yet."