Ok, so if you have permanent 12V/ground on the correct wires, then I'd suggest a couple of things...
When turning on the radio, do you still get the option of DSP when you scroll through the settings? if so, then it could mean the head unit is still in DSP mode and you may need to totally unplug the power from the head unit, and then power it back up/input code etc. I'm not sure how it detects the DSP amp to switch between modes (it obviously looks for communications on the I-bus line - but whether it only 'refreshes' once the head unit has been fully powered off/on or whether it does it on any power up, I'm not 100% sure as i've always done my testing on the bench where I can turn the power off fully).
If you don't get the option of DSP, then chances are it's already just outputting normally in non-DSP mode. in this case, I would then try testing the amps separately.
I test my amps on the bench, just with a 3.5mm jack and then connecting one side of this (Left or Right, doesn't matter) to the input pins of the amplifier and then play some music through my mp3 player. As long as the amp is powered up with 12V, gnd, and then 12v switched on the grey/black wire, then you should hear something through the speakers for that amp.
I have a few amps here which are faulty - they don't seem to power up fully when the switched 12V is provided, and if I jumper the amplifier chip manually, then it powers up and works - so there must be a component on the amp board which is causing it to not turn on fully. That being said.. I would find it very strange if NO speakers work...
'06 4.2 Supercharged Black/Cream "Jess" -- Bought April 2021 (NZ)
'01 4.6 Vogue Black/Lightstone "Snog" -- Bought Jan 2012
'99 4.6 HSE Cobar Blue/Lightstone -- Sold March 2009
'95 4.6 HSE Epsom Green/Tan -- Traded June 2008