如果您无法下载和安装任何插件，并且由于Firefox浏览器上的连接失败而收到错误无法^{(he add-on could not be downloaded because of a connection failure)}下载^(T)插件，那么您仍然可以下载和安装它。发生错误是因为服务器没有响应用户提出的请求。

由于连接失败，无法下载加载项

1]手动下载扩展^{(1] Manually Download Extension)}

就在我们开始之前，由于我们正在下载文件，我建议使用下载管理器。如果出现问题，您可以恢复下载。

1. 打开加载项^(Add-on)页面并查找添加^(Add)到Firefox按钮。如果您使用的是第三方网站，请查找下载链接。
2. 右键单击^{(Right-click)}下载链接^(Download)或添加^(Add)到Firefox按钮。选择另存为^{(Save as)}。
3. 它将保存为.xpi文件。您可以选择默认名称或添加您的名称。
4. 按^(Press)Enter按钮开始下载。
5. 下载完成后，如果询问，请选择使用Firefox打开它。插件将被安装。如果没有，您可以选择使用Firefox打开。

2]启用xpinstall标志^{(2] Enable xpinstall flag)}

1. 转到about:config 然后单击 “我会小心我保证”^{(“I’ll be careful I promise”)} 按钮。
2. 键入xpinstall.enabled以查找设置
3. 双击将值设置为true

虽然这两个应该足以在连接失败的情况下下载扩展程序，但有时您需要等待。这可能是一个临时问题，可以自行解决。最后，我会推荐使用VPN软件^{(VPN software)}。如果您的ISP 阻止^{(ISP is blocking)}了任何内容，则VPN连接应该能够解决。

我希望您能够解决此问题，并摆脱错误消息 - 由于连接失败而无法下载加载项- Firefox错误。

The add-on could not be downloaded because of a connection failure

If you cannot download and install аny addon and уou receive an error The add-on could not be downloaded because of a connection failure on your Firefox browser, then here is how you can still download and install it.  The error occurs because the server is not responding to the request made by the user.

The add-on could not be downloaded because of a connection failure

1] Manually Download Extension

Just before we start, since we are downloading a file, I will suggest using a download manager. In case of issues, you can resume the download.

1. Open the Add-on page and look for Add to Firefox button. If you are using a third party website, look for the download link.
2. Right-click on the Download link or Add to Firefox button. Select Save as.
3. It will get saved as a .xpi file. You can choose the default name or add your name.
4. Press the Enter button to start the download.
5. Once the download is complete, If asked, opt to open it with Firefox. The addon will get installed. If not, you can choose to open with Firefox.

2] Enable xpinstall flag

1. Go to about:config then click on “I’ll be careful I promise” button.
2. Type xpinstall.enabled to find the settings
3. Double click to set the value to true

While these two should be enough to download the extension in case of a connection failure, sometimes you need to wait. It could be a temporary issue that gets resolved on its own. In the end, I will recommend using VPN software. If there is anything that your ISP is blocking, the VPN connection should be able to resolve.

I hope you were able to fix the issue, and get rid of the error message—The add-on could not be downloaded because of a connection failure – Firefox error.

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