Thunderbird Won't Open: 4 Fix if it has Stopped Working

Mozilla Thunderbird is one of the most trusted email clients on the market, available on various platforms used not only as an email client but also as an RSS feed and much more. And the best part? It’s an open-source project.

However, even though this email client is frequently updated and well-coded, users are experiencing several issues with the software.

One is critical, and it’s related to sudden crashes after startup. For this purpose, we prepared a simple but helpful workaround that should help you resolve it.

Why won’t Thunderbird open?

If you have issues opening Thunderbird, there are a few elements that users have attributed to this. Some of them include the following:

• Outdated software version – If the software is outdated, you will need a new version to respond properly.
• Insufficient resources – In some cases, users may have run out of device storage. This will mean some applications will cease to respond.
• Corrupted profile – If the user profile has been corrupted, you generally will have issues using certain applications, including Thunderbird.
• Firewall or antivirus issues – Users have experienced that, at times, the firewall may block out the Thunderbird app.
• Corrupted files – If the software installation file has been corrupted, you will likely face a few bugs, including difficulty starting the application.

Although a solid email client, many users reported that Thunderbird wouldn’t open on their PC. This can be an issue. Speaking of Thunderbird, here are some similar issues reported by users:

• Thunderbird not responding – Many users reported that Thunderbird isn’t responding at all. This can be due to your Thunderbird profile, but you can fix that by deleting parent.lock file.
• Thunderbird won’t start/ missing profile in Safe Mode – These Thunderbird issues can appear on any version of Windows, but even if you don’t use Windows 10, you should know that most of our solutions can be applied to both Windows 8.1 and 7.
• Thunderbird won’t start already running – If you’re getting this error message, open Task Manager and close all Thunderbird instances. After doing that, try to start the application again.
• Thunderbird won’t launch – Many users reported that it wouldn’t launch on their PC. This can be a problem, but you can fix it simply by running Thunderbird in Safe Mode.
• Thunderbird won’t start after crash – Sometimes, a crash can damage your Thunderbird profile, and to fix that, try reinstalling the application.

What can I do if Thunderbird won’t open?

Before trying our fixes, you should restart and reset your modem. Several users reported that they fixed the issue with Thunderbird simply by restarting their modem. This is relatively simple, and to do it, you need to press the Power button on your modem, wait for a few seconds and then turn it back on again.

You can also consider switching to a different email client. For example, if the previous solution didn’t fix the problem with Thunderbird, this might be an excellent time to consider switching to a different email client.

Many great email clients are available, but if you want one similar to Thunderbird, we recommend you try Mailbird.

Due to its seamless integration with other email clients like Gmail and Outlook, Mailbird is one of the best software options on the market.

You can quickly transfer complicated schedules from your calendar and also add contacts from other third-party software, allowing you not to worry about your data not being compatible.

Or, as an alternative, use a portable version of the app. This version doesn’t require installation, and it won’t add any information to the registry so the previous Thunderbird installation won’t affect it in any way.

Once you download the portable version, run it and check if that solves your problem. If the issue doesn’t appear, you might have to switch to the Portable version until you fix the problem.

1. Delete parent.lock file

1. Close Mozilla Thunderbird.
2. Right-click on the Taskbar and open Task Manager.
   
3. Under Processes, find and kill all Thunderbird-related processes.
4. Press the Windows key + R to bring up the Run command.
5. Type %appdata% in the command line and press Enter.
   
6. Open the Thunderbird profile folder.
7. Find and delete the parent.lock file. You may need administrative permission to do so.
8. Start Thunderbird again. It should now function without any problems.

These steps should also correct any issues with your Thunderbird user profile in case it is corrupted.

2. Reinstall Thunderbird

1. Press Windows + R, type appwiz.cpl, and hit Enter.
   
2. Search for Thunderbird from the app list, click it, and hit the Uninstall button.
   
3. Follow the wizard to complete the uninstallation.
4. Visit the Thunderbird website.
5. Click on the Free Download button.
   
6. Double-click on the downloaded file and follow the wizard to complete the installation.

According to users, sometimes Thunderbird won’t open if your installation is damaged. This can be a big problem, but one of the easiest ways to fix the issue is to reinstall Thunderbird. There are several ways to do that, and you can do it right from the Settings app.

We recommend you use dedicated software to uninstall Thunderbird. Sometimes, uninstalling from the UI or the settings app can leave behind unwanted files.

Not only will these files take up space on your PC for no reason, but they may also prevent you from reinstalling the app and creating all sorts of errors in your system.

We suggest you look into the best uninstaller software and pick your best bet. They are specifically created to remove stubborn programs along with lingering files.

On top of that, many of them include additional PC optimization features that keep your system clean and high-functioning.

3. Start Windows in Safe Mode

1. Press Windows Key + I to open the Settings app.
2. Go to Update & Security section.
   
3. In the left pane, select Recovery. In the right pane, click Restart now in the Advanced startup section.
   
4. Now select Troubleshoot, then Advanced options.
   
5. Click on Startup Settings, then Restart.
   
6. Once your PC restarts, you’ll have a list of options. Press F5 or 5 to select Safe Mode with Networking.

Once you start Windows in Safe Mode, try to rerun Thunderbird. If the issue still exists, start Thunderbird in Safe Mode and check if that helps.

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4. Start Thunderbird in Safe Mode

1. Press Windows + R to bring up the Run command.
2. Type thunderbird -safe-mode and press Enter.
   

If you want a more user-friendly way to start Thunderbird in Safe Mode, locate the Thunderbird shortcut, press and hold the Shift key and start the application.

After doing that, a new window will appear. Just click Continue in Safe Mode to start the Thunderbird. If the issue doesn’t appear, your add-ons or toolbars are causing it.

To permanently fix the problem, repeat the process, but this time check Disable all add-ons and Reset toolbars and controls. Now click the Make Changes and Restart button.

This is useful if your configuration or third-party add-ons cause the issue. For example, Thunderbird supports a wide array of add-ons allowing you to enhance its functionality. Still, sometimes specific add-ons can interfere with your system and prevent you from starting Thunderbird.

Hopefully, your email client now works. However, if you have any remarks or questions regarding the subject, use the comments section below!