The only reason I can think of for the no bail and rearrest is if he has a new case. He would not be able to bail out once sentenced anyway so that doesn't apply to this case. Contact his attorney.
I am guessing based on the few facts you have given us but it sounds like your son was out of custody until sentencing at which time he was remanded (rearrested). I do not understand why there would be a no bail notation as while he is serving his time he is not eligible for bail anyway. Does he have a second case? That would explain the rearrest no bail notation.