How to fix the Runtime Code 421 Service not available

Symptoms of Code 421 - Service not available

Runtime errors happen without warning. The error message can come up the screen anytime Mozilla Thunderbird is run. In fact, the error message or some other dialogue box can come up again and again if not addressed early on.

There may be instances of files deletion or new files appearing. Though this symptom is largely due to virus infection, it can be attributed as a symptom for runtime error, as virus infection is one of the causes for runtime error. User may also experience a sudden drop in internet connection speed, yet again, this is not always the case.

(For illustrative purposes only)

Causes of Service not available - Code 421

During software design, programmers code anticipating the occurrence of errors. However, there are no perfect designs, as errors can be expected even with the best program design. Glitches can happen during runtime if a certain error is not experienced and addressed during design and testing.

Runtime errors are generally caused by incompatible programs running at the same time. It may also occur because of memory problem, a bad graphics driver or virus infection. Whatever the case may be, the problem must be resolved immediately to avoid further problems. Here are ways to remedy the error.

Repair Methods

Runtime errors may be annoying and persistent, but it is not totally hopeless, repairs are available. Here are ways to do it.

If a repair method works for you, please click the upvote button to the left of the answer, this will let other users know which repair method is currently working the best.

Please note: Neither ErrorVault.com nor it's writers claim responsibility for the results of the actions taken from employing any of the repair methods listed on this page - you complete these steps at your own risk.

Method 1 - Close Conflicting Programs

up vote 0 down vote

When you get a runtime error, keep in mind that it is happening due to programs that are conflicting with each other. The first thing you can do to resolve the problem is to stop these conflicting programs.

• Open Task Manager by clicking Ctrl-Alt-Del at the same time. This will let you see the list of programs currently running.
• Go to the Processes tab and stop the programs one by one by highlighting each program and clicking the End Process buttom.
• You will need to observe if the error message will reoccur each time you stop a process.
• Once you get to identify which program is causing the error, you may go ahead with the next troubleshooting step, reinstalling the application.

Method 2 - Update / Reinstall Conflicting Programs

up vote 0 down vote

Using Control Panel

• For Windows 7, click the Start Button, then click Control panel, then Uninstall a program
• For Windows 8, click the Start Button, then scroll down and click More Settings, then click Control panel > Uninstall a program.
• For Windows 10, just type Control Panel on the search box and click the result, then click Uninstall a program
• Once inside Programs and Features, click the problem program and click Update or Uninstall.
• If you chose to update, then you will just need to follow the prompt to complete the process, however if you chose to Uninstall, you will follow the prompt to uninstall and then re-download or use the application's installation disk to reinstall the program.

Using Other Methods

• For Windows 7, you may find the list of all installed programs when you click Start and scroll your mouse over the list that appear on the tab. You may see on that list utility for uninstalling the program. You may go ahead and uninstall using utilities available in this tab.
• For Windows 10, you may click Start, then Settings, then choose Apps.
• Scroll down to see the list of Apps and features installed in your computer.
• Click the Program which is causing the runtime error, then you may choose to uninstall or click Advanced options to reset the application.

Method 3 - Update your Virus protection program or download and install the latest Windows Update

up vote 0 down vote

Virus infection causing runtime error on your computer must immediately be prevented, quarantined or deleted. Make sure you update your virus program and run a thorough scan of the computer or, run Windows update so you can get the latest virus definition and fix.

Method 4 - Re-install Runtime Libraries

up vote 0 down vote

You might be getting the error because of an update, like the MS Visual C++ package which might not be installed properly or completely. What you can do then is to uninstall the current package and install a fresh copy.

• Uninstall the package by going to Programs and Features, find and highlight the Microsoft Visual C++ Redistributable Package.
• Click Uninstall on top of the list, and when it is done, reboot your computer.
• Download the latest redistributable package from Microsoft then install it.

Method 5 - Run Disk Cleanup

up vote 0 down vote

You might also be experiencing runtime error because of a very low free space on your computer.

• You should consider backing up your files and freeing up space on your hard drive
• You can also clear your cache and reboot your computer
• You can also run Disk Cleanup, open your explorer window and right click your main directory (this is usually C: )
• Click Properties and then click Disk Cleanup

Method 6 - Reinstall Your Graphics Driver

up vote 0 down vote

If the error is related to a bad graphics driver, then you may do the following:

• Open your Device Manager, locate the graphics driver
• Right click the video card driver then click uninstall, then restart your computer

Method 7 - IE related Runtime Error

up vote 0 down vote

If the error you are getting is related to the Internet Explorer, you may do the following:

1. Reset your browser.
• For Windows 7, you may click Start, go to Control Panel, then click Internet Options on the left side. Then you can click Advanced tab then click the Reset button.
• For Windows 8 and 10, you may click search and type Internet Options, then go to Advanced tab and click Reset.
2. Disable script debugging and error notifications.
• On the same Internet Options window, you may go to Advanced tab and look for Disable script debugging
• Put a check mark on the radio button
• At the same time, uncheck the "Display a Notification about every Script Error" item and then click Apply and OK, then reboot your computer.

If these quick fixes do not work, you can always backup files and run repair reinstall on your computer. However, you can do that later when the solutions listed here did not do the job.

Other languages:

Wie beheben Fehler 421 (Dienst nicht verfügbar) - Dienst nicht verfügbar. Der Server wird heruntergefahren.
Come fissare Errore 421 (Servizio non disponibile) - Servizio non disponibile. Il server è spento.
Hoe maak je Fout 421 (Service niet beschikbaar) - Service niet beschikbaar. De server wordt afgesloten.
Comment réparer Erreur 421 (Service non disponible) - Service non disponible. Le serveur est arrêté.
어떻게 고치는 지 오류 421 (서비스를 사용할 수 없음) - 서비스를 사용할 수 없습니다. 서버가 종료되었습니다.
Como corrigir o Erro 421 (Serviço não disponível) - Serviço não disponível. O servidor está encerrado.
Hur man åtgärdar Fel 421 (Tjänsten är inte tillgänglig) - Tjänsten är inte tillgänglig. Servern stängs av.
Как исправить Ошибка 421 (Услуга не доступна) - Услуга не доступна. Сервер выключен.
Jak naprawić Błąd 421 (Usługa niedostępna) - Usługa niedostępna. Serwer jest wyłączony.
Cómo arreglar Error 421 (Servicio no disponible) - Servicio no disponible. El servidor está apagado.

About The Author: Phil Hart has been a Microsoft Community Contributor since 2010. With a current point score over 100,000, they've contributed more than 3000 answers in the Microsoft Support forums and have created almost 200 new help articles in the Technet Wiki.

Follow Us: