Downloading .config did not succeed

Error:

- Downloading blah/blah/xyz.exe.config did not succeed

- Downloading .config did not succeed

PLATFORM VERSION INFO
Windows : 6.2.9200.0 (Win32NT)
Common Language Runtime : 4.0.30319.34003
System.Deployment.dll : 4.0.30319.33440 built by: FX45W81RTMREL
clr.dll : 4.0.30319.34003 built by: FX45W81RTMGDR
dfdll.dll : 4.0.30319.33440 built by: FX45W81RTMREL
dfshim.dll : 6.3.9600.16384 (winblue_rtm.130821-1623)

SOURCES
Deployment url : http://xyz.com/download/xyz.application
Server : Microsoft-IIS/7.5
X-Powered-By : ASP.NET
Deployment Provider url : http://xyz.com/download/xyz.application
Application url : http://xyz.com/download/Application%20Files/xyz_2_3_1_0/xyz.exe.manifest
Server : Microsoft-IIS/7.5
X-Powered-By : ASP.NET

IDENTITIES
Deployment Identity : xyz.application, Version=2.3.1.0, Culture=neutral, PublicKeyToken=91eae35baf867b49, processorArchitecture=msil
Application Identity : xyz.exe, Version=2.3.1.0, Culture=neutral, PublicKeyToken=91eae35baf867b49, processorArchitecture=msil, type=win32

APPLICATION SUMMARY
* Installable application.

ERROR SUMMARY
Below is a summary of the errors, details of these errors are listed later in the log.
* Activation of http://xyz.com/download/xyz.application resulted in exception. Following failure messages were detected:
+ Downloading http://xyz.com/download/Application Files/xyz_2_3_1_0/xyz.exe.config did not succeed.
+ The remote server returned an error: (404) Not Found.

COMPONENT STORE TRANSACTION FAILURE SUMMARY
No transaction error was detected.

WARNINGS
There were no warnings during this operation.

OPERATION PROGRESS STATUS
* [7/13/2014 11:00:18 AM] : Activation of http://xyz.com/download/xyz.application has started.
* [7/13/2014 11:00:21 AM] : Processing of deployment manifest has successfully completed.
* [7/13/2014 11:00:21 AM] : Installation of the application has started.
* [7/13/2014 11:00:32 AM] : Processing of application manifest has successfully completed.
* [7/13/2014 11:00:49 AM] : Found compatible runtime version 4.0.30319.
* [7/13/2014 11:00:49 AM] : Request of trust and detection of platform is complete.

ERROR DETAILS
Following errors were detected during this operation.
* [7/13/2014 11:01:26 AM] System.Deployment.Application.DeploymentDownloadException (Unknown subtype)
- Downloading http://xyz.com/download/Application Files/xyz_2_3_1_0/xyz.exe.config did not succeed.
- Source: System.Deployment
- Stack trace:
at System.Deployment.Application.SystemNetDownloader.DownloadSingleFile(DownloadQueueItem next)
at System.Deployment.Application.SystemNetDownloader.DownloadAllFiles()
at System.Deployment.Application.FileDownloader.Download(SubscriptionState subState)
at System.Deployment.Application.DownloadManager.DownloadDependencies(SubscriptionState subState, AssemblyManifest deployManifest, AssemblyManifest appManifest, Uri sourceUriBase, String targetDirectory, String group, IDownloadNotification notification, DownloadOptions options)
at System.Deployment.Application.ApplicationActivator.DownloadApplication(SubscriptionState subState, ActivationDescription actDesc, Int64 transactionId, TempDirectory& downloadTemp)
at System.Deployment.Application.ApplicationActivator.InstallApplication(SubscriptionState& subState, ActivationDescription actDesc)
at System.Deployment.Application.ApplicationActivator.PerformDeploymentActivation(Uri activationUri, Boolean isShortcut, String textualSubId, String deploymentProviderUrlFromExtension, BrowserSettings browserSettings, String& errorPageUrl)
at System.Deployment.Application.ApplicationActivator.ActivateDeploymentWorker(Object state)
--- Inner Exception ---
System.Net.WebException
- The remote server returned an error: (404) Not Found.
- Source: System
- Stack trace:
at System.Net.HttpWebRequest.GetResponse()
at System.Deployment.Application.SystemNetDownloader.DownloadSingleFile(DownloadQueueItem next)

COMPONENT STORE TRANSACTION DETAILS
No transaction information is available.

Solution:

This error related to IIS security about .config files. you must go to your visual studio Project > Properties > Publish > Options > and checked Use '.deploy' file extension checkbox ;-)