The most likely solution is that your voltage is dropping too much and the amp is going into protect mode to save itself because of the lack of power. Double check fuses in the amp first and then on the power cable and third make sure all the connections are solid, i.e. ground and power wire. Another thing might be to check that you didn't switch the polarity by connecting negative and positive wires to their opposites.
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The most likely solution is that your voltage is dropping too much and the amp is going into protect mode to save itself because of the lack of power. Double check fuses in the amp first and then on the power cable and third make sure all the connections are solid, i.e. ground and power wire. Another thing might be to check that you didn't switch the polarity by connecting negative and positive wires to their opposites.