All of a sudden my hazards stopped working

Hi I really need some help I have a fiat cinquecento and I had my cd player fitted and all of a sudden my hazards stopped working my indicators are fine its just the hazards and if I turn my hazards on nothing happens and I can not turn my indicators on at the same time I have tried a new switch and I tuck it back to where I had my stereo fitted and they unplugged the stereo and that did nothing I tried a new relay switch and still nothing I really need some help as my car will not pass its mot without the hazards thank you very much alana gask