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

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).

Answer 1

[MathWorks Support Team]

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.