My Kindle says Critical Battery & I have plugged it in overnite & it still says this but I have it on the computer now & the light is on on the on switch so not sure what this means? is it charging or what

Try These Troubleshooting steps to fix kindle critical battery error. I hope these steps will help you.

Solution 1: Connect the Charger Properly

A Connect the original charger to the device and plug another end into the power outlet.
B See if the charging LED indicator turns ON. In case the light doesn't lit up; remove the cable, and plugin it again.
C Once the device starts charging let it charge for at least a few hours (four to five hours). Your device should be fully charged.

Solution 2: Use the Power Button

A Keep your charging cable connected to your device and the power outlet.
B While your device is charging; long-press the "Power button" for at least one minute.
C Release the button when your kindle turns off. Now, unplug the charger from the device and the outlet.
D Reconnect the charger to the device and the outlet again.
E In case it is not, try doing this steps, again and again, i.e., removing and reconnecting the power USB cable.

Solution 3: Use Recovery Mode

A Remove the USB cord from the device and the outlet, then slide the "power button" to the right side.
B Keep holding in this position for at least 20 seconds and release the power slide.
C Next, press and long hold the Home key for at least 30 - 45 seconds.
D The Kindle's screen will start flashing.
E Now, release the Home key.
F Once your kindle is completely rebooted; plug in the USB charging cable again.

if you need any help then you can read this blog:
https://kindlehelpguides.com/fix-kindle-critical-battery-error

I actually found a solution for this error.
https://www.errorsolutions.tech/error/kindle-critical-battery-error/
follow solutions No.2 it works for me perfectly for me.

Hi!

You can try these steps to solve this problem:

1. Connect Kindle to a different USB.
2. Verify the charge light at the base of the Kindle is on.
3. Restart Kindle by pressing Home > Menu > Settings > Menu and select "Restart."
4. Leave the unit charging for 30 minutes

If the problem persist, contact Kindle for repair options.

eBookBoy