Notebook won't turn on

Your battery is probably not working anymore. Go to an apple store and ask for the repair.

Buy a new battery, may show as fully charged but does not output to laptop, i had same problem bought new battery fault solved.

The System / Motherboard has faulty Power Circuit. Contact HP and arrange a repair. If under warranty won't cost anything.

Let the battery completely discharge all they way and let it sit for a day or so. Some times when a battery is new most user do not let it fully charge and then completely drain this causes problems for long use batteries. Then give it a try. It also sounds like your plug your cord that connects to the battery may be faulty. Did you by a different cord with the battery? Or use the one from your old one? If you did. This is a "No No" always buy the cord that come for those battery since they are rated for the particular battery.

Batteries don't always look degraded but if they've been in use for a while or have a bad cell, they will show up bad on the charger and it won't charge them. The only way to test the batteries is to try to charge them on another charger. If the batteries show defective on another charger, they are bad and you'll have to replace them. Also try to charge some batteries you know to be good on your charger to see if it's the problem. If your batteries charge on another charger, your current charger is bad and they don't have any replaceable parts in them so you'd be looking at replacing it.

Laptops are so integrated that usually a system failure that involves power issues such as in your case where you cant get it turn on with anything on the screen mean the mainboard (motherboard) is damaged. This usually leads to buying a new laptop or paying for the board to be replaced which usually costs as much as the laptop.

I would look into testing the laptop by taking out the battery and plugging in solely the charger, and try turning it on. If it doesn't work, it sounds like it can probably be an issue with the Motherboard or the RAM.

Is the blinking light an amber or green color? If amber, then it might be a RAM issue. If green, the power would be on, but the monitor might not be active/working.

Try removeing the battery form the laptop and using just AC porwer. if it still fails you may need to replace the motherboard. :(

The diagnostic procedures from the Dell User Guide are as follows:

Total Power Failure When Using a Battery
If an AC adapter is not connected to your computer, the computer's power source
is a battery. If the battery indicator flashes amber or is a steady amber, the
battery needs to be charged. If the battery is flashing green and amber, the
battery may be defective. To troubleshoot this problem, use the following
procedure.
1. Turn off the computer and peripherals, and disconnect them from AC power.
2. Reseat each installed battery by removing it and then replacing it.
3. Turn on the computer. Does the green power indicator light up?
Allow one minute for the computer to initialize its components before checking
for signs of power.
Yes. Continue to step 4.
No. Use the AC adapter to connect your computer to AC power. If the computer
operates normally when using AC power, go to step 7. If the computer does not
boot when using the AC adapter, see the previous subsection, "Total Power
Failure When Using the AC Adapter."
4. Does the battery indicator flash amber or show a a steady amber light?
Yes. The battery needs to be charged. Go step 5.
No. Go to step 7.
5. Connect the computer to AC power, and fully charge the battery.
For instructions, see the topic titled "Charging the Battery" in the online
System User's Guide.
6. As the battery charges, does the green battery indicator light up?
Yes. Go to step 9.
No. Go to step 7.
7. Is the battery indicator flashing green and amber?
Yes. Your computer may be in a hot environment. Charging the battery in this
condition may affect the life span of the battery. Continue to step 8.
No. The problem is resolved.
8. Disconnect the computer from AC power. Is the the battery indicator still
flashing amber?
Yes. You may have a defective battery. Continue to step 9.
No. The problem is resolved.
9. Remove the battery, and press its test button. Is the uppermost indicator in
the charge gauge of the battery flashing?
Yes. You have a defective battery. Continue to step 9.
No. The problem is resolved.
10. If a spare battery is available, fully charge it, and then install it in the
computer.
11. Turn on the computer. Is the power indicator off?
Yes. Your original battery is defective


good luck