Have you matched the wattage of the lamps to the max wattage output of the transformer - if not could be transformer blown due to overload.
If not could be loose connection in junction box on supply cables to trnsfmrs - check you have supply to all trnsfmrs - live AND neutral.
Its got to be something simple if they were working 1 day ago - too much of a coincidence to be all lamps gone but do check.
Post back if still not working after you've checked all of the above.
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