No power geting to my subwoofer from my head unit,also no bass gain on my amplifier !!

It sounds like your amplifier may be clipping, which can cause distortion and eventually damage your subwoofers. This can happen if you turn the gain or bass boost too high, or if you are pushing the amp beyond its rated power.
Here are a few things you can try:

1. Check the wiring: Make sure that the positive and negative speaker wires are securely connected to the amplifier and the subwoofers, and that there are no loose or damaged connections.
2. Adjust the gain: Turn down the gain on the amplifier to reduce the amount of power being sent to the subwoofers. Start with a low setting and gradually increase it until the subs are playing at a comfortable volume.
3. Check the bass boost: If your amplifier has a bass boost feature, turn it off or reduce it to a low setting. This can also cause the amplifier to clip and damage the subs.
4. Check the impedance: Make sure that the subwoofers are wired to the correct impedance for your amplifier. Wiring them incorrectly can cause the amp to overheat and shut off.

If none of these solutions work, you may need to have your amplifier and subwoofers checked by a professional.

To prevent clipping, you need to turn down the gain or bass boost on your amplifier. The reason this is happening is because the head unit is telling to put out a certain amount of power, and the amplifier, well... amplifies it based on your gain level. Reducing the gain should stop the clipping.

Where is your subwoofer gain set? Also, what crossover frequency do you have the sub set to?

set gain to match head unit.its not a volume control.turn bass up.on unit and amp.and not knocking what you have but sony well theres much better.

Well, make sure that the output level on your head unit is up, and also try adjusting the gain NEVER EVER PUT IT ON FULL GAIN BECAUSE THAT WILL CLIP THE AMP AND MAY BLOW AMP AND/OR SUB!!!

Is this powering speakers or subwoofer? If it's the subwoofer you need to make sure the gain is turned up and the sub is set to low pass frequency. Also make sure bass and subwoofer are enabled on the head deck. Make sure the RCA's are hooked up properly at the back of the head deck. If it's the speakers then you may have balance set to front only so your rear speakers aren't making noise.

Make sure the subwoofer is set to low frequency, make sure subwoofer and bass are enabled on the headdeck. Make sure the gain is turned up on the amp, make sure the rcas haven't come out of the back of the head deck.

Check RCA,s at the back of the head deck, make sure sub is set to low bass frequency, make sure gain is turned up on the amp and head deck has subwoofer enabled and bass on. If you are powering speakers make sure the balance on the head deck is set to 0. Make sure it's wired up properly.

make sure all your gains are turned up to atleast half.
Check your head unit, make sure your low pass frequency for the RCA's amp is set to high or set to more than 0. Make sure you don't have your fader set toward the front of the vehicle or you won't get any bass, but the subwoofer will be pulling only what the head unit is sending to the amplifier.
if that doesn't work I would try another pair of patch cables.
Do you have another subwoofer you can swap out to test your subwoofer with?
I have a subwoofer that has something wrong with the coil itself. Has your amplifier blown any fuses? If so the subwoofer coil is bad.
Also make sure you have a solid ground for your amplifier.
Hope this helps!

What head unit do you have?
Is there a dedicated subwoofer output?
If not, have you switched the rear output to sub output?
Is the amplifier set to LPF (low pass filter), and the gain turned up?
Many things can be wrong, but the fact that there is anything coming out of the subs is a good thing.
Start at the beginning - Head unit, then check amplifier gain/crossover setting.
If you are using a hi level adapter on factory radio, is the Bass on the radio up? is the output gain on the convertor up?