If the amp gain looks good and the sub is OK, a possibility would be that the Sub Max Volume setting in the Fusion HU is set close to zero...
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2017 Moomba Craz Surf Edition
Flow 2.0 Surf System w/ AutoWake™
5,600 Lbs Ballast - Enzos + Lead + Sumo
Wet Sounds REV10s + REVO12-XXX