All outdoor lights were working fine until I mulched the garden area where the lights are placed. None of them work now.

Mulch did not damage the low voltage lights. You need to check the connection at the distribution box. Check the watts on the bulbs and add them up; it should equal or be less that the transformer wattage. If its greater than the transformer output then that is your issue. Take out some lights or purchase a larger transformer. Ensure contacts on tightening knob make good contact with low voltage wire as a last option.

Hello and Thank you for your question. Usually there is no need to dig up any of the lighting. You can always call our customer service department for trouble shooting tips. 1-800-643-0067. 1) Check to see if a power surge caused the transformer to turn itself Off automatically. This can be done by pushing the built in circuit breaker button on the front of the transformer that comes with the kit. During the daytime turn the transformer onto the ON position, then push the circuit breaker button. This should turn the lights On. Once they turn On you can then set the transformer to the desired setting. Always make sure that the transformer has power. 2) If you have the transformer plugged into an outdoor rated power receptacle that is a GFCI. Check to see if the receptacle needs to be reset. There should be a button you can push on the receptacle if it is a GFCI. You can hear the transformer turn On once power is going to the transformer.