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Installation of NetExtender plugin fails in Mozilla Firefox and Google Chrome
03/26/2020 
1,101 People found this article helpful
481,620 Views
Description
In Mozilla Firefox, the error - The add-on could not be downloaded because of a connection failure on .... - is displayed when trying to install the NetExtender plugin. This error occurs when SonicWall UTM SSL-VPN is configured to use the default SonicWall self-signed certificate, or a certificate signed by a private CA, as opposed to a certificate signed by a public CA (Thawte, Versign etc.). Firefox does not allow plugin installations over SSL (HTTPS) if the certificate issuer (CA) is not a built-in certificate present in it's certificate store.
In the case of Google Chrome, the error - Apps, extensions, and user scripts cannot be added from this website. - is displayed when trying to install the NetExtender plugin. This error occurs because Google Chrome does not allow adding extensions unless it is in the Chrome Web Store or if the user manually installs extensions by adding them through the Extensions page of Chrome.
Resolution
Google Chrome
Chrome while refusing to install the add-on, downloads the plugin file - npNLChrome.crx. Follow these steps to install the file manually:
- Navigate to the Tools | Extensions page.
- Drag and drop the downloaded file - npNLChrome.crx - into the Extensions page.
- Click on the NetExtender icon to install the NetExtender plugin.
Mozilla Firefox
Any one of the following workarounds can be implemented for Firefox browsers:
- 1. Obtain and import a certificate signed by a public CA and use the certificate for SSL-VPN connection.
- 2. Add a new user preference in the about:config page to bypass the built-in CA restriction. After the plugin has been installed, this preference can be Reset later to deactivate it. To add a new preference, follow these steps:
WARNING: This is not recommended by SonicWall and is listed here as an option which users may choose to implement at their own risk.
- Right-click anywhere in the list of preferences.
- In the context menu, select New then select Boolean
- Enter preference name (case sensitive) - extensions.install.requireBuiltInCerts
- Select boolean value as false
- Click on OK.
- Double-click (or right-click toggle) on app.update.cert.requireBuiltIn to set its value to false.
- Restart the browser.
- Click on the NetExtender icon to install the NetExtender plugin.
ISSUE ID:
122941
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