There maybe a setting on the HU that needs to be enabled. Go to Auto zone and buy a $4.99 test light. Ground 1 end and touch the red post on the amp, does it light up? With the HU on touch the blue post, does it light up? If I had to guess having a 60A fuse would be the same as having no fuse at all I think your wires would melt before the fuse popped.