How to troubleshoot Protocol Negotiation Failed in TeamViewer?

TeamViewer is great software that allows you to connect to a remote PC. The tool comes in handy if you travel a lot and still want to transfer files, photos, or any other documents remotely. The TeamViewer app is preferred by many users for its simplicity and advanced features. However, some users are getting the “Protocol Negotiation Failed. Please try again.” error message every time they try to establish a connection to a remote desktop.

Understandably, this can be quite frustrating if you want to transfer important documents or you need to connect to a client’s desktop to complete a project. Luckily, in this post, you’ll find several workarounds on how to resolve the TeamViewer “Protocol Negotiation Failed” error when remote control is not working.

What causes the “Protocol Negotiation Failed” error message in TeamViewer?

The “Protocol Negotiation Failed” error occurs when a certain process in your system is interfering with the connection of TeamViewer. As a result, TeamViewer fails to establish a connection with the host. Some of the reasons that could trigger the error when trying to connect to a remote desktop include:

• Malware: a malware attack can cause havoc on your PC and trigger a myriad of errors, including BSOD errors.
• TeamViewer is outdated: if you’re running a different version of TeamViewer than the one on the remote computer, it might trigger the “Protocol Negotiation Failed” error message.
• Windows Firewall: changes made to the Windows Firewall, whether intentional or not, might be blocking the incoming and outgoing requests sent by TeamViewer.
• Third-party antivirus: if you’ve installed third-party antivirus software, it’s worth checking if it’s interrupting the connection of the TeamViewer app.

How to fix ‘Protocol Negotiation Failed’ in TeamViewer

Fix 1: Temporarily disable your antivirus software

While third-party antivirus software may have more functionality and provide more security features than the built-in Windows Defender, sometimes the antivirus might block some settings that it’s not supposed to.

For this reason, try disabling your third-party antivirus software to check if you can establish a connection using TeamViewer. If you can connect to the remote desktop, then your antivirus is to blame. What you’ll need to do is add an exception to allow TeamViewer to work.

Fix 2: Scan for malware infection

Viruses and malware are known to alter certain processes and settings on your PC, which could block TeamViewer from establishing a connection. As such, you’ll be better off scanning your computer to check if it has been infected.

To do so, you can run the built-in Windows Security software, Windows Defender, or install powerful third-party anti-malware software.

To use Windows Defender:

1. Press the Win + I shortcut keys to launch “Settings”.
2. Open “Update & Security”.
3. Go to the “Windows Security” tab.
4. Click on the “Virus & threat protection” link to open it.
5. Open the “Scan options” link.
6. Select the “Full Scan” radio button, and click on “Scan now”. For a deeper scan, select the “Windows Defender Offline scan” option, and then click the “Scan now” button.
7. Wait until the process completes, and then try to log into the TeamViewer app to establish a connection.

In addition, you could exclude the TeamViewer folder from being scanned by Windows Defender. To do so:

1. Go to “Virus & threat protection” in the “Settings” app, and select the “Manage settings” link under “Virus & threat protection settings”.
2. Locate the “Exclusions” section, and select the “Add or remove exclusions” link.
3. Select “Add an exclusion”, and click on the “Folder” option.
4. Find the “TeamViewer” folder and click on it.
5. Click on “Select folder”.
6. Click “Yes”.

If this fails, try a more advanced anti-malware tool like Auslogics Anti-Malware. This is an innovative security program that features three types of PC scans, namely Quick Scan, Deep Scan, and Custom Scan. These features offer a comprehensive analysis of the system memory, temporary folders, auto-start items, and browser extensions to check for suspicious items and protect your system against security threats.
Unlike other antivirus software, Auslogics Anti-Malware is designed to detect malware that is developed to infiltrate computers without detection. The software has a straightforward user interface, making it easy to use.

Fix 3: Update TeamViewer

For any program to run properly, it needs to be updated regularly. Software developers release updates periodically to fix bugs and add new functionalities. If you’re trying to connect your TeamViewer app to a remote desktop that’s using a different version of TeamViewer, then the connection might drop. So, make sure to update the TeamViewer app to the latest version on both computers.

Fix 4: Flush DNS

Occasionally, a corrupt local DNS cache may make it difficult to connect to a website or server, leading to errors like ‘Protocol Negotiation Failed’ in TeamViewer. If that’s the case, flushing Windows DNS cache will allow your PC to establish a connection with the host. To flush DNS:

1. Press the Windows Key, and type Command Prompt.
2. Right-click the top result, and select “Run as administrator”. Alternatively, select “Run as administrator” on the right pane.
3. Execute the following commands, one after the other:
   • ipconfig/release
   • ipconfig/renew
   • ipconfig/flushdns
4. Exit the “Command Prompt” window and try to use TeamViewer to connect remotely again.

Fix 5: Allow TeamViewer through Windows Firewall

Windows 10 comes with an array of security features designed to block malicious apps that could harm your PC from interfering with your operating system. However, sometimes the Windows Firewall can block out some apps that you normally use, such as Skype or TeamViewer.

Luckily, there’s a workaround that allows you to bypass the firewall so that you can use your favorite apps. To allow TeamViewer through the Windows Firewall, do the following:

1. Click the “Start” menu, and type Windows Security.
2. Select the top result to open the “Windows Security” window.
3. Open the “Firewall & network protection” option.
4. Click on the “Allow an app through firewall” link.
5. Click the “Change Settings” button.
6. Locate TeamViewer in the list of apps.
7. Check the box under “Private” if you want to allow TeamViewer to connect to the internet only at home or work. Alternatively, check the box under “Public” if you want to allow TeamViewer to connect to the internet from anywhere, even using public Wi-Fi hotspots, which are less secure.
8. Click “OK”.

This should resolve the issue and allow TeamViewer to connect to the host.

We hope you could resolve the TeamViewer ‘Protocol Negotiation Failed’ error when trying to connect to a remote desktop. If you’re still getting the error message, reach out to us for expert assistance by leaving your comments below.