How to fix error 633 the modem is already in use or not configured properly

Imagine this scenario: You’re working from home, racing against a deadline, and suddenly your internet connection drops. You hastily check your modem, only to be greeted with a cryptic message: “Error 633: The modem is already in use or is not configured properly.” Panic sets in as your productivity grinds to a halt. In today’s digital age, such disruptions can be costly and frustrating. However, fear not! In this article, we’ll explore the reasons behind this error, common error codes, and provide a comprehensive guide on how to fix Error 633, both automatically and manually.

Understanding the Problem

Error 633 is a common issue encountered by users when trying to establish a connection using a modem. It can occur due to a variety of reasons, including conflicts with other devices or software on your computer. Understanding the possible causes of this error is the first step toward resolving it.

Common Reasons for Error 633

  1. Modem Already in Use: The error’s most straightforward interpretation is that your modem is already being utilized by another program or process on your computer. This often happens when background applications, such as automatic updates, seize control of the modem.
  2. Incorrect Modem Configuration: If your modem’s settings are incorrect or outdated, it can trigger Error 633. This may include issues with the COM port settings, driver problems, or outdated firmware.
  3. Software Conflicts: Incompatible software or drivers can interfere with your modem’s operation. This can be caused by recent software installations, updates, or third-party applications.
  4. Hardware Issues: Sometimes, hardware problems like loose connections, damaged cables, or a malfunctioning modem can be at the root of Error 633.

Common Error Codes

Error messages often come with numerical codes, which can provide clues about the nature of the issue. Here are some common error codes associated with modem-related problems:

  • Error 619: The specified port is not connected.
  • Error 678: There is no answer.
  • Error 680: There is no dial tone.
  • Error 691: Access denied because the username and/or password is invalid.

How to Fix Error 633

Now that we’ve identified potential causes and some related error codes, let’s delve into the steps to resolve Error 633.

Automatic Fixes

  1. Restart Your Computer: Begin with the simplest solution. A simple reboot can terminate background processes and clear up conflicts.
  2. Update Modem Drivers: Outdated or corrupted modem drivers can be a common culprit. Visit the manufacturer’s website and download the latest drivers for your modem.
  3. Run Troubleshooter: Most modern operating systems include a built-in network troubleshooter. Running it can automatically identify and fix common modem issues.

Manual Fixes

  1. Check for Background Applications: Press Ctrl+Shift+Esc to open the Task Manager. Look for any applications that might be using the modem and close them.
  2. Reconfigure COM Port Settings:
    • Go to the Device Manager.
    • Under “Ports (COM & LPT),” right-click on your modem and select “Properties.”
    • Navigate to the “Port Settings” tab and click “Advanced.”
    • Change the COM port to a different number, if available, and click “OK.”
  3. Reset Modem and Reconnect: Physically unplug your modem, wait for a minute, and then plug it back in. Reconnect and try establishing a connection.
  4. Check Hardware Connections: Ensure that all cables and connections between your modem, computer, and telephone line are secure and undamaged.
  5. Disable Conflicting Software: Temporarily uninstall or disable any recently installed software or drivers that might be causing conflicts.


Error 633 can be a vexing roadblock, but armed with knowledge and a systematic approach, you can swiftly overcome it. Troubleshooting modem issues is often a matter of elimination and patience. Whether it’s a simple restart, updating drivers, or reconfiguring settings, there are multiple paths to a solution.

However, if the error persists despite your best efforts, it might be wise to consult your internet service provider (ISP) or the modem manufacturer for further assistance.

Remember, maintaining a healthy and well-configured modem is essential for seamless internet connectivity, especially in our digitally dependent lives.


Q1: Can Error 633 occur on mobile devices? A1: While Error 633 is more commonly associated with traditional modems, similar issues can affect mobile data connections. The troubleshooting steps may differ slightly, so consult your device’s documentation or your mobile carrier for guidance.

Q2: What if I can’t find updated drivers for my modem? A2: In some cases, modem manufacturers may stop providing driver updates for older models. In such instances, consider contacting the manufacturer’s support for assistance or explore community forums for possible workarounds.

Q3: Can antivirus software cause Error 633? A3: Yes, certain antivirus or security software can interfere with modem operations. Temporarily disabling such software can help diagnose whether it’s the cause of the problem.

Q4: Is it safe to change COM port settings manually? A4: Changing COM port settings should be done with caution. Always make a note of the original settings, and if possible, consult your modem’s documentation or support resources for guidance on proper configuration. Incorrect settings could lead to further issues.

Q5: What if Error 633 occurs intermittently? A5: If the error is intermittent, it might be related to specific software or background processes that occasionally seize control of your modem. Review your recently installed or updated software for potential culprits and monitor when the error occurs to pinpoint the cause.

Sakshi Anant Author