My ipad pro suddenly has area i can't draw.

Hello Willbrisz,

Thank you for reaching out to Apple Support Communities.

Let's erase and pair your Apple Pencil again using these steps:

If your Apple Pencil won't pair with your iPad

1. Make sure to center your Apple Pencil (2nd generation) on the magnetic connector on the right edge of the iPad. For an Apple Pencil (1st generation), remove the cap and plug your Apple Pencil into the Lightning connector on your iPad.
2. Restart your iPad, then try to pair again.
3. Go to Settings > Bluetooth and make sure that Bluetooth is turned on.
4. On the same screen, look under My Devices for your Apple Pencil. If you see it, tap . Then tap Forget this Device.
5. Connect your Apple Pencil in to your iPad and tap the Pair button when it appears after a few seconds. 
6. If you don't see the Pair button, wait for one minute while your Apple Pencil charges. Then try connecting your Apple Pencil again and wait until you see the Pair button.
7. If you still don’t see the Pair button, contact Apple Support.

More details can be found here: Connect Apple Pencil with your iPad

If the issue persists, can you provide a few more details? When did you first notice this? What is your exact iPadOS version? Which Apple Pencil do you have? Also, are you able to test with another iPad or Apple Pencil?

Good Luck!