Factory reset iPad mini causing setup issues for new owner

Perhaps the iPad was not properly erased by you prior to selling the device. See:

What to do before you sell, give away or trade in your iPhone or iPad – Apple Support

Follow the section entitled "if you no longer have your iPhone or iPad".

If the new owner of your iPad mini is having difficulty setting it up after you factory reset it, here are the key steps you or the new owner should check and do:

1. Make sure the iPad is completely erased: Go to Settings > General > Transfer or Reset iPad > Erase All Content and Settings. Confirm the passcode if prompted to ensure the device is fully reset to factory conditions.
2. Confirm Activation Lock is disabled: If Find My iPad was enabled before the reset, the iPad will ask for your Apple ID and password to disable Activation Lock during setup. You need to sign out of your Apple ID before selling or give the new owner the Apple ID credentials temporarily to bypass this.
3. If the iPad gets stuck during setup or shows an error, try putting it into recovery mode and restoring via a computer:

• • Connect the iPad to a Mac or PC with iTunes (or Finder on macOS Catalina and later).
  • Follow the button presses to enter recovery mode (usually holding Home and Power buttons until the recovery screen appears).
  • Choose Restore to reinstall iPadOS and complete the setup fresh.

1. Restart the device or perform a soft reset if it seems frozen during setup.
2. The new owner should follow the on-screen setup prompts carefully, connecting to Wi-Fi and signing in with their own Apple ID after Activation Lock is cleared.

If the problem is Activation Lock or forgotten Apple ID details, the new owner won't be able to fully use the device until those are resolved. Otherwise, performing a factory reset and restore via recovery mode usually clears most setup issues.