MATLAB: Do I get the error ERR_TUNNEL​_CONNECTIO​N_FAILED (-111) when using App Designer or other web-based applications in MATLAB

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I am trying to open App Designer in MATLAB R2019a. An App Designer window pops up with the following error message:
Unable to open the requested feature.
Check your internet connection and proxy settings in MATLAB Web preferences and then try starting the feature again.
Detailed information:
Error code: -111
Error message: ERR_TUNNEL_CONNECTION_FAILED
The same error messages appears when I open Add-On Explorer.
When invoking the Documentation through the Help menu, the error message is:
Failed to load URL <...> with error ERR_TUNNEL_CONNECTION_FAILED (-111).

Best Answer

We have seen this issue with workflows involving web-based applications such as the Add-On Explorer, App Designer, Live Editor or Simulink Diagnostic Viewer.
The underlying reason is likely because of a proxy setting in the VPN. Please try out the following steps:
1) Disable proxy setting in MATLAB:
  • Navigate to Home > Preferences > Web.
  • Uncheck "Use a proxy server to connect to the internet".
  • Check whether this resolves the issue.
2) If you are connected to a VPN, try disabling it to see if it resolves the issue.
3) Make sure you firewall/antivirus software does not block MATLAB.
4) Upgrade your MATLAB to R2019b or later.
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