A device doesn't recognize the handwriting with S Pen

Remove any third-party cases or covers. 

• Too hard or rubbery surface for writing.
• An uneven surface, which affects consistency.
• The thickness of a screen protector can affect screen sensitivity.
• A dirty or old screen protector can affect performance.
• Remove the screen protector and retest the S Pen.

Replace the S Pen tip.

If the pointer appears on the screen, but no touches are recognized, the tip may need to be changed. If your S Pen came with replacements you can change the S Pen tip. 

To replace the S Pen tip, take out the existing nib by firmly holding it and pull it out with the tweezers included in the box. Then gently insert the new nip into the S Pen. Make sure not to use excessive force in the process.

Be sure to check if your device's software is updated with the latest version. Please check how to update your mobile device's software in the following order. 

Step 1. Go to Settings > Software update.

Step 2. Tap on Download and install. 

Step 3. Follow the on-screen instructions.

You can also update the software via Smart Switch.

Press and hold the Volume Down and Power key for 7 to 10 seconds to perform a forced reboot or soft reset. On phones without a dedicated Power key, press and hold the Volume down key and Side key for 7 to 10 seconds.

The part where the navigation bar and app screen meet at the bottom of the screen is not touchable by Android OS’s policy. This phenomenon is not a device defect.

Here are some tips if the S Pen is being recognized everywhere except for at the bottom of the screen:

• Tap or touch the bottom portion of the screen slowly when using the S Pen. 
• Turn off Block gestures with S Pen. Navigate to Settings >  Display > Navigation bar. Under Swipe gestures, tap the switch next to Block gestures with S pen to turn this off.
• Set the navigation type to Navigation buttons. For this, navigate to Settings > Display > Navigation bar > Buttons. Then try using the S Pen.