I forgot screen time passcode

If you have forgotten the ScreenTime passcode, one of the two procedures outlined within this link should resolve the problem:

If you forgot your Screen Time passcode - Apple Support

If your iPad is capable of supporting iPadOS 13.x or later, you should update to the most current version before attempting to resolve a forgotten ScreenTime passcode. The most recent iPadOS updates have introduced a new mechanism whereby a forgotten ScreenTime passcode can be reset without wiping the iPad.

To reset a forgotten ScreenTime passcode on older versions of iOS/iPadOS, the iPad must be reset “as new”, losing all locally stored data. In this situation, you’ll not be able to restore your data from an iCloud or iTunes backup - as the forgotten passcode is integral to the backup.

I hope this information is helpful to you in successfully resetting your forgotten passcode.

Did you do this? Note you have to tap Change Screen Time Passcode twice.

On an iPhone, iPad, or iPod touch

1. Make sure that your device is updated to iOS 13.4 or iPadOS 13.4 or later. 
2. Go to Settings > Screen Time. 
3. Tap Change Screen Time Passcode, then tap Change Screen Time Passcode again.
4. Tap Forgot Passcode?
5. 
6. 
   
7. Enter the Apple ID and password* that you used to set up the Screen Time passcode.
8. Enter a new Screen Time passcode, then enter it again to confirm.

If still have problem I would first restart the device and try again

Restart your iPad - Apple Support

If still problem then you will have to erase the device and resetup the iPad. If the backup contains the screentime passcode then you will have to setup as new.