troubleshooting source error (#5370)

<!-- To check a checkbox place an "x" between the brackets. e.g: [x] -->

- [x] I have signed the [Contributor License
Agreement](https://cla.opensource.microsoft.com/microsoft/winget-pkgs).
- [x] This pull request is related to an issue.

-----

Resolves #5368 
###### Microsoft Reviewers: [Open in
CodeFlow](https://microsoft.github.io/open-pr/?codeflow=https://github.com/microsoft/winget-cli/pull/5370)

Author: denelon

doc/troubleshooting/README.md

@@ -153,3 +153,9 @@ A possible troubleshooting step is to install the [KB5005565](https://support.mi
 #### Updating Microsoft.DesktopAppInstaller from version 1.0.42251.0 doesn't render package name on Windows 11 Pro image in Azure
 
 Launching the Microsoft.DesktopAppInstaller update on Windows 11 Pro image in Azure to update from version 1.0.42251.0 might not render the correct package name title. The workaround to this issue is to install the latest Microsoft.DesktopAppInstaller with Windows Package Manager.
+
+#### Failed in attempting to update the source: winget
+
+The WinGet Community repository (a.k.a. "winget" source) requires network connectivity to https://cdn.winget.microsoft.com/cache. Depending on the version of WinGet, either the source.msix or source2.msix is downloaded and installed. This pre-indexed package contains the local copy of metadata queried by WinGet. 
+
+If running `winget source update` doesn't resolve the problem and you are on WinGet 1.10 or newer, you may be able to correct the problem by uninstalling the current source "Windows Package Manager Source (winget) V2" and running another winget command, or manually install the source from: https://cdn.winget.microsoft.com/cache/source2.msix (You may need to download this using "In Private" if you encounter a 404).