[2025] Fix ‘TeamViewer Protocol Negotiation Failed’ on Windows/Mac

“I cannot connect to any of my computers nor can I do file transfers to them. Every time I try, I get a ‘protocol negotiation failed’ error message” (TeamViewer Support Forum)

It’s common to encounter TeamViewer connectivity issues when trying to secure access to a remote desktop. The “Protocol Negotiation Failed” error indicates a component on your system is interrupting the TeamViewer connection request.

But fret not! This article explores numerous solutions to resolve the TeamViewer protocol negotiation failed error on Windows/Mac.

Solutions to Fix Protocol Negotiation Failed

Moreover, you can rely on a TeamViewer alternative tool for a hassle-free and effective remote working experience.

Part 1: Common Causes of “Protocol Negotiation Failed” Error in TeamViewer

When the error message “TeamViewer protocol negotiation failed” pops up, look for the below factors:

Firewall Configuration: The security settings on your Windows firewall of the antivirus software might be blocking the TeamViewer connection.

Outdated TeamViewer: If you’re using different versions of the TeamViewer app on the local and remote devices, it can trigger the “Protocol Negotiation Failed” error.

System Glitches: A minor bug in the TeamViewer app or any program running in the background might hinder the remote connection.

Software Incompatibility: An outdated operating system software on either device also hinders the proper functioning of TeamViewer.

Based on these reasons, we will present an array of solutions to help you resolve the issue.

Part 2: Quick Ways to Troubleshoot TeamViewer Protocol Negotiation Failed

Implement the below solutions to resolve the TeamViewer connectivity issues.

Solution 1: Update TeamViewer

The inability of TeamViewer to launch the remote session is often due to the mismatched TeamViewer app version on either machine. Make sure the program is up-to-date on both devices as demonstrated below:

Step 1: Open the TeamViewer app.

Step 2: Click the three-dots icon > Check for the new version.

Step 3: Install the updates, if available.

Solution 2: Restart TeamViewer Services

Sometimes, a minor glitch in the TeamViewer app running in the background is the reason behind the “TeamViewer protocol negotiation failed on Mac.” The best option is to restart the TeamViewer program.

On Windows:

Step 1: Press the Windows + R keys to open up Run.

Step 2: Type in services.msc.

Step 3: Find and right-click TeamViewer and hit Restart.

On Mac:

Step 1: On the Apple Menu, select Force Quit.

Step 2: Select the TeamViewer app.

Step 3: Relaunch the app.

Solution 3: Update Windows/Mac Software

Do you have any pending updates on Windows/Mac? The next solution is to install all the available updates on your machine, both local and remote.

For Windows:

Step 1: Head to Settings and select Windows Update at the bottom.

Step 2: Click Check for Updates.

Step 3: Install the updates.

For Mac:

Step 1: Search for “Software Update” in the menu bar.

Step 2: It will begin checking for the new updates.

Step 3: Hit “Update Now” to proceed.

Solution 4: Temporarily disable your antivirus software

The security apparatus on your machine often blocks the incoming connection request, leading to “TeamViewer protocol negotiation failed.” To check this, disable the Windows firewall or antivirus program temporarily on the remote device.

Step 1: On Windows, open Control Panel.

Step 2: Go to System and Security > Windows Defender Firewall.

Step 3: Select “Turn Windows Defender Firewall on or off” on the left plane and turn it off under both Public and Private options.

Step 4: Similarly, disable the third-party security software, if running, on your Windows or Mac.

Now, try connecting to the remote PC. If it connects, then the security firewall is to blame.

Solution 5: Allow TeamViewer Through Firewall

In this solution, you must configure the firewall settings to allow TeamViewer to pass through it. Luckily, you can allow any third-party app to bypass the firewall, as shown below:

Step 1: Open Control Panel and go to System and Security > Windows Defender Firewall.

Step 2: Now, click Allow an app or feature through Windows Defender Firewall on the left plane.

Step 3: Click Change Settings and find TeamViewer in the list of apps.

Step 4: Tick both "Private" and "Public" options. 

Moreover, if you’re using a third-party antivirus tool on your Windows/Mac, configure its settings make an exception for TeamViewer.

1. Simply, open the Settings > Exclusions

2. Search for the TeamViewer installed file path.

3. Select the whole folder to add it to the Excluded list. 

Now, try connecting to the remote device again. Hopefully, you won’t encounter the “TeamViewer protocol negotiation failed” error.

Solution 6: Disable IPV6 Protocol

If the issue is in the Network settings, try turning off the IPV6 protocol temporarily. This solution works especially for Windows users to restore the functioning of TeamViewer. To use it:

Step 1: From the Control Panel, go to Network and Internet > Network and Sharing Center > Change Adapter Settings.

Step 2: Right-click your network adapter and select Properties.

Step 3: On the pop-up menu, find and uncheck the “Internet Protocol Version 6 (TCP/IPv6)” option.

Step 4: Click ok to save the changes. This is likely to fix your problem immediately.

Part 3: Other Troubleshooting Methods

Here are several additional ways to restore the TeamViewer’s remote connection functionality.

Solution 1: Flush DNS

Sometimes, a corrupt file in the DNS cache makes it difficult for the system to connect to the remote connection. If not addressed, it can lead to errors like ‘Protocol Negotiation Failed’ in TeamViewer. So, you need to clear the DNS cache on both computers.

To do that:

Step 1: Search for command prompt, right-click the top-most option, and select “Run as administrator”.

Step 2: Execute the below commands one by one:

ipconfig/release

ipconfig/renew

ipconfig/flushdns

Step 3: Now, close the command prompt window and try to use the TeamViewer remote connection again.

Solution 2: Scan your PC for Malware Infection

The issue of “TeamViewer protocol negotiation failed” occurs if your PC has a virus or malware infection. In such a scenario, the best option is to thoroughly scan the device to remove the infected files.

Now, you can run the Windows Defender or any third-party antivirus tool to search for malware. Here are the steps to run a scan in Windows 10:

Step 1: Go to Windows Security > Virus & Threat protection. 

Step 2: Click Scan options and select Full scan. Hit Scan now to proceed. 

Step 3: Wait until the process is finished.

TeamViewer Alternative: Get Error-Free Remote Connection

If none of the above tips has solved the issue or you just want to explore more efficient TeamViewer alternatives, try AirDroid Remote Support. This multi-feature program is designed to offer a fast remote connection without any connectivity errors.

It is incredibly easy to use for everyone without needing a prior knowledge. Having over a million active users, AirDroid is known for stellar remote control features, including unattended access, file transfer, and voice chat, real-time screen sharing, and a remote camera for Android/iOS devices.

Additionally, users can control multiple remote devices from a single, intuitive interface.  All these features make it an ideal solution to handle your personal and business remote tasks with greater productivity.

FAQs

Q1: Which protocol does TeamViewer use?

TeamViewer relies on the TCP and RDP connections over port 5938. Thus, if this port is blocked by the firewall, you’re likely to encounter connectivity issues.  

Q2: Is TeamViewer safe from hackers?

As TeamViewer uses the advanced 256 Bit AES session encoding, it’s pretty much safe from hackers. However, you should set a strong password especially when enabling the “unattended mode” feature.

Final Remarks

This post outlines numerous solutions to fix the "TeamViewer Protocol Negotiation Failed" error. It shouldn’t take you much longer to deal with such TeamViewer remote connectivity issues. However, if you’re tired of frequent troubles, we recommend you use an alternative like AirDroid Remote Support.

It guarantees a stable, secure, and error-free remote working experience coupled with more advanced and rich functionality. Try this wonderful product and let us know if you have any queries.