The lights were working fine and all at once quit and none of them would come back on. What are some reasons the entire light kit would quit working?

Hello and Thank you for your question. 1) If you have the transformers plugged into a GFCI outlet, then check the GFCI outlet to see if it needs to be reset. Simply press the button on the GFCI receptacle. The GFCI outlet if working properly will protect the transformer from power surges. 2) You can always use a 12 volt multimeter to check if power is coming from the transformer. If power is coming from the transformer, then it can allow power to move through the low voltage cable. You can also use the 12 volt multimeter to check the low voltage cable as well. If power is present, then check to see if bulbs are not blown out. Lowes sells these bulbs in the same isle as the low voltage landscape fixtures. Simply look for Lowes Item No. 157139.

you could have had a sudden surge in power and blown all the bulbs or shorted out the transformer, check some of the bulbs then use volt meter at the end of wire for voltage.