Laptop will not turn on

I have an HP dv4 laptop that is about 16 months old. Friday night it just suddenly shut off and I have not been able to turn the laptop on since then. When the AC adapter is plugged in, there is a light on the side of the laptop that is lit, but the lights on the front that indicate it is charging the battery or on are not lit. If I hit the power button, it will flash one time, then both that and the light on the side will go out and won't come back on unless I unplug the adapter, wait 15-20 seconds, and plug it back in. But the laptop still never turns on, no fans running or anything to indicate it's even trying to boot.

I tried buying a new AC adapter but still have the same problem. I tried taking out the battery and adapter and holding the power button for 30 seconds but still no luck. I don't know what else it could be. I haven't been able to find any answers from HP and the warranty just expired. Looking for any kind of help I can get.

 

was the battery almost flat when it went off?

I had a similar problem with a an external drive. If the power supply is in 2 parts, with a converter to drop the voltage, it is could be that, but probably not, unless you are really unlucky with the new one.
If you have other cables, or can try the existing ones with another device, see if that works.