ipad won't say on. the logo comes on then it goes off

Start by connecting your iPad to its Power Adapter and allow the iPad to charge for at least an hour. This step is advised as a battery with very low charge, or is failing, may produce symptoms that emulate a boot loop.

If the problem fails to stabilise after an hour, whilst still connected to the Power Adapter, attempt a forced restart of the iPad:

• On an iPad with a Home button: Press and hold the top button and the Home button at the same time. When the Apple logo appears, release both buttons.
• On other iPad models: Press and quickly release the volume up button, press and quickly release the volume down button, then press and hold the top button. When the Apple logo appears, release the button.

If iPad still doesn’t turn on, or if it gets stuck during start up, see the Apple Support article If your iPhone, iPad, or iPod touch won't turn on or is frozen. Or if your iPad isn’t working correctly after you restart it, see the iPad Support website.

If your iPad is stuck is actually stuck in a boot-loop, you’ll need to resolve this specific issue - which may entail “restoring” the most recent version of iPadOS to the iPad. This support page outlines restoration of an iPad to Factory Settings:

Restore your iPhone, iPad or iPod to factory settings – Apple Support

You’ll need access to either a PC (with iTunes installed) or a Mac (with iTunes or Finder - as appropriate for the installed version of MacOS).

Download and use iTunes for Windows – Apple Support

Update to the latest version of iTunes – Apple Support

Use of a PC or Mac computer is unavoidable. If you don’t have access to a suitable computer of your own, that of a helpful friend or family member will suffice. Alternatively, the technicians at the Genius Bar of your local Apple Store or Apple Authorised Service Provider (AASP) will be delighted to assist.

For iPad models with a Home button, do a simple hard reset of your iPad by holding down both the Home and sleep/wake/power button simultaneously until your iPad goes to black and restarts with Apple logo, then release the buttons.

OR

For much newer design iPad models, without a Home button, try the new simple hard reset procedure for the new 2018/2020/2021 iPad Pros, 2020 iPad Air 4 and 2021 iPad Mini 6 models.

1. Press and release the volume up button.

2. Then immediately press and release the volume down button.

3. Then, press and hold the single sleep/wake/power button You will see the Slide to Power off button, but keep on holding down the power button until you see the Apple logo, then let it go.

Once you have performed all the steps, wait for a few seconds and your 2018 iPad Pro will boot up completely to the iPad Pro’s Lock screen.

Best of Luck to You!