It's perfectly normal to have to retune a guitar every day. You may also have to retune occasionally whilst playing.

As for the tuner not finding the D string, how fresh are the batteries in the tuner?

Another way to get the string close is compare it with the A string pressed on the 5th fret. It's the same note, although it will sound a little different. The tuner should then be able to find the D string. Another possible cause for the tuner not finding it could be you are plucking it too hard or too soft for the tuner to register the vibrations correctly.