---
title: Common Issues and How to Fix Them on Your CommBox Classic S4
description: Having issues with your CommBox Classic S4? This guide covers common problems and easy solutions—from power issues to display and connectivity fixes.
---

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1. [Knowledge Base](https://support.commbox.com.au/knowledge?hsLang=en)
2. [CommBox Classic S4](https://support.commbox.com.au/knowledge/commbox-classic-s4?hsLang=en)
3. [How to](https://support.commbox.com.au/knowledge/commbox-classic-s4?hsLang=en#how-to)

# Common Issues and How to Fix Them on Your CommBox Classic S4

## Running into problems with your CommBox? Here’s a quick guide to common issues that are easy to troubleshoot on your own—plus when to contact CommBox Support.

#### Applies To

**Applies to:** Classic S4, Classic S4+

#### Lock Screen or Settings PIN Forgotten

**Issue:** You’ve forgotten the lock screen or settings PIN  
**Solution:**

- Read this article first - [What to do if you don't know the PIN](https://support.commbox.com.au/knowledge/what-do-i-do-if-im-prompted-for-an-unknown-pin-on-my-commbox-s4?hsLang=en)
- If still stuck Contact CommBox Support at **+61 2 9975 6001** for assistance

#### Wi-Fi Issues (5 GHz Not Connecting)

**Issue:** The CommBox can't connect to a 5 GHz Wi-Fi network  
**Solutions:**

- The Wi-Fi module may not be installed correctly—check that it's securely connected underneath the screen
- Some 5 GHz bands may not be supported—ask your IT administrator to review the network settings

💡 **Note:** 5 GHz has shorter range and may be blocked by walls or large metal objects. Try a 2.4 GHz network instead.

#### Stylus Missing or Damaged

**Issue:** A stylus pen is broken or lost  
**Solution:**

- [Order new Stylus online at Karter.](https://karter.com.au/products/commbox-classic-s4-s4-stylus-pen-set)

#### Missing or Unavailable Apps

**Issue:** An app isn’t showing or can’t be installed  
**Solutions:**

- The app may not be able to run on Android 11.
- **Note:** Apps requiring Google Play Services (e.g. Google Play Store) are not supported

#### The CommBox Won’t Turn On

##### No Status Light

- Check that the power cable is firmly plugged in
- If using a power board, ensure it’s switched on
- Make sure the **main power switch** (next to the AC inlet) is set to the **“I” (on)** position
- Test the power outlet with another device
- Try a different power cable if available

##### Red Light On, But Screen is Blank

- Press the **Power** button on the screen or remote

##### Green Light On, But Screen is Blank

- Wait 30 seconds after powering on
- Disconnect anything plugged into **HDMI OUT** ports
- Restart the CommBox

#### The CommBox Turns Off Unexpectedly

**Issue:** The screen powers down or enters standby too soon  
**Solutions:**

- Check the **power-off timer** in Settings
- Review the **auto no-signal** power-saving setting
- If connected via **RS-232** (e.g. room control system), temporarily disconnect it and test again

#### Screen Display Problems

##### Blank Screen (Green Light On)

- Ensure connected computers are **powered on and not in standby**
- Restart both the CommBox and the computer
- Try different video cables
- Check that the computer is outputting a supported resolution (recommended: **3840×2160** or **1920×1080**)
- Ensure the computer's external display port is enabled

##### “No Signal” Message

- Confirm the computer is connected to the correct input
- Make sure the input source selected on the CommBox matches the port used
- Enable external display output on your laptop
- Use only CommBox-recommended video cables

##### Distorted, Flickering, or Dim Image

- Switch to another input, then switch back
- Restart the CommBox and any connected devices
- Confirm the resolution and refresh rate on your computer match supported settings
- Replace or test with new video cables
- If these tips do not resolve it - [contact CommBox Support.](https://support.commbox.com.au/knowledge/kb-tickets/new?hsLang=en)

##### Bright Spots or Colour Issues

- Try adjusting the image mode in **Settings \> Image**
- Small colour variation is normal between side-by-side displays
- If using VGA, test with another cable or source
- If these tips do not resolve it - [contact CommBox Support.](https://support.commbox.com.au/knowledge/kb-tickets/new?hsLang=en)

##### Image Shifted or Cropped

- Adjust video output settings on your computer (zoom, crop, overscan)
- Use a darker background instead of black
- If using multiple monitors, try duplicating the display or setting the CommBox as the only screen

##### Image Doesn't Fill the Screen

- Adjust the overscan or scaling settings on the connected device
- Make sure the output resolution is supported by the CommBox

##### No Video from USB-C

- Confirm the device supports **CommBox Port Alternate Mode** via USB-C
- Look for the **Thunderbolt logo**—if missing, full video+touch may not be supported
- Use a cable marked for **SuperSpeed (5 Gbps or higher)** with the **USB logo**
- Replace the cable if not compliant

#### Still Need Help?

📩 [Log a support ticket](https://support.commbox.com.au/knowledge/kb-tickets/new?hsLang=en) or call **+61 2 9975 6001. If you want faster support remember to provide video or photographic evidence of the issue.** 

 

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