Have you checked that the radio is receiving a signal, my wife's 2015 Polo does things like that when the DAB signal is lost, and you can't just change from local to national station groups and get any sound, the older radios used to drop out of DAB when there was not a signal and change to the FM version of same station if possible, switching the radio off and back on when back in a known good DAB regional station coverage always works.