To reset winhttp back, run the following command: netsh winhttp reset proxy 2 other reasons why you might receive the same error code.
1 - It could be the Local System cannot authenticate to your web proxy.
“Local System” might not be able to connect to the internet for a variety of reasons, but the most common appears to be when your company is using manual proxy settings in the web browser.
When you configure manual proxy settings for your users, it doesn't effect the “Local System” account, rather Local System is always set to “Automatically detect settings”.
2 - You might be updating from a local file share, and local system doesn't have rights to the local file.
This is a text file, placed on a web server on your network, which holds configuration as to which proxy server(s) to use, for which end points.
[Update: this article was updated on 15 April 2014.
As information about the second scenario has changed from an Office build issue, to a Office Deployment Tool issue] There are several reasons why your Office 365 Pro Plus might fail with the error, error code: 30088-27.
By manually adding the key, updating started to work (as long as you are not a victim of the “Local System” issue too). You should have 1 of the following keys (just having one of them works, you don't need both).
The value should be set to the path where updates are retrieved from.
This allows you to specify which IPs / Host Names are internal, and gives greater flexibility than the manual settings you probably have today anyway.