Press and hold the power button and the volume up button together for about 10 seconds until the screen goes black, then wait for the phone to restart on its own or press the power button to turn it back on. This force restart is the quickest way to clear a temporary software glitch that's freezing the touchscreen. I'd start with this one, as it works for most random touchscreen freezes without affecting your data.
Clean the Screen Thoroughly
Turn the phone off and wipe the screen with a clean, slightly damp microfiber cloth. Smudges, grease, or moisture from your hands can sometimes confuse the touch sensors, especially on the Nord 4's smooth display. Make sure to dry it completely before turning the phone back on.
If you've recently applied a new screen protector, check for air bubbles or improper alignment. A poorly fitted protector is a very common cause of unresponsive touch areas. Peel it off and test the bare screen to see if the problem goes away.
Check for Physical Damage or Interference
Inspect the screen closely for any new cracks, even small ones. Damage to the digitizer layer underneath the glass can cause dead spots. Also, check if the phone is unusually hot; the metal unibody is great for heat dissipation, but extreme heat from prolonged gaming or direct sun can temporarily affect screen sensitivity.
Remove any third-party case, especially thick or metal ones. Sometimes a case can press on the edges of the screen or cause interference. Test the touch response with the phone bare to rule this out.
Boot Into Safe Mode
This checks if a recently downloaded app is causing the problem. First, press and hold the power button until the power off menu appears. Then, tap and hold the "Power off" option on your screen until you see a prompt to reboot to Safe Mode.
Tap "OK" to restart. If the touchscreen works perfectly in Safe Mode (you'll see "Safe Mode" in the bottom corner), you have a problematic app. Restart normally to exit Safe Mode and try uninstalling apps you installed just before the issue started.
Update Your Software
An outdated system can have bugs that affect touch response. Plug your Nord 4 into its included 100W SuperVOOC charger to ensure it has plenty of power. Then, go to Settings > About device > OxygenOS version and tap "Check for update."
If an update is available, download and install it. These updates often include patches for known issues. For the fastest data transfer if you're sideloading, remember to use a USB-C to USB-C cable, not the included USB-A to USB-C charging cable.
Calibrate the Touchscreen
While OxygenOS doesn't have a built-in public calibration tool, you can use a hidden diagnostic menu. Open your phone dialer and enter *#808# to launch the engineering mode test menu. Navigate to "Touch Panel Test" or a similar option.
Follow the on-screen instructions, which usually involve tracing patterns or tapping specific points. This test can sometimes reset the touchscreen drivers. Be careful not to change any other settings in this menu.
Perform a Factory Reset
This erases all your personal data, so it's a last resort. First, back up everything important. Then, with the phone powered off, press and hold the volume down and power buttons together until the OnePlus logo appears.
Use the volume buttons to navigate to "Wipe data and cache" and select it with the power button. Choose "Erase everything" to confirm. After the reset, set up the phone as new to see if the touch issue is resolved by a clean software install.
Consider a Hardware Fault
If the screen is completely dead to touch even in recovery mode or after a factory reset, the issue is likely physical. The Nord 4's metal build is durable, but a drop can still damage the internal digitizer connector or the screen assembly itself.
Since the phone lacks an official IP rating, previous exposure to moisture or spills could also lead to corrosion over time. In these cases, the solution would involve a professional repair to inspect or replace the screen component.