Maps and Apps Gallery shows "Loading Maps and Apps..." and no items appear

Description

When accessing the ArcGIS for Local Government Maps and Apps Gallery, the gallery section shows the message:

 'Loading Maps and Apps...' but fails to load the gallery items after several minutes.

Cause

The application is not able to access the ArcGIS Online group containing the items for the application's gallery.

Solution or Workaround

Note:
As of April 2018, the Maps and Apps Gallery app template is in the Mature Phase of the ArcGIS Online Product Lifecycle. For more information regarding support of this app template, refer to the Maps and Apps Gallery requirements page.

It is recommended to use the Minimal Gallery app template instead.

The following terms are defined for reference when diagnosing the problem.

• Group refers to an ArcGIS Online group. A Maps and Apps Gallery is linked to a single group. The group may be public or private, and the group may be a normal account or an ArcGIS for Organizations account.
• Group ID refers to the unique code used by ArcGIS Online to identify the group.

Note:
For example, the try-it live version of the Maps and Apps Gallery is linked to the ArcGIS Online Group ID a3031224716a4624a224c00dd629d199.

• Token refers to the ArcGIS access token that is generated using Token Helper, the target Maps and Apps Gallery URL, and the ArcGIS Online Group owner's ArcGIS Online login name and password.

Note:
The token occasionally ends in one or more periods ‘.’ -- these are essential parts of the token. ArcGIS Online login names and passwords are case-sensitive.

The following steps describe how to diagnose the problem.

1. Verify that the ArcGIS Online token was generated using the target Maps and Apps Gallery URL.

Note:
For example, the token for the try it live version of the Maps and Apps Gallery uses 'http://localgovtemplates2.esri.com/MapsAndApps'.

2. Use the Group ID Helper to check the Group ID and token. Enter the group owner's ArcGIS Online login name and the token to see a list of the ArcGIS Online groups owned by that user. The group that is being used for the Maps and Apps Gallery must appear in this list, and its ID must match the ID used in the application's configuration/config.txt file.
3. In the Internet Information Services (IIS) management application, check that the target Maps and Apps site has been converted to an application and that the site is using the DefaultAppPool.

Note:
In IIS 6, the latter can be checked by selecting the site and clicking on Base parameters in the rightmost column of IIS's management application.

4. Verify that the site's web.config does not contain the line:

<compilation targetFramework="4.0"/>

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <system.webServer>
        <defaultDocument>
            <files>
                <remove value="iisstart.htm" />
                <remove value="index.html" />
                <remove value="index.htm" />
                <remove value="Default.asp" />
                <remove value="Default.htm" />
                <remove value="Default.aspx" />
                <add value="mapps.html" />
            </files>
        </defaultDocument>
    </system.webServer>
</configuration>

5. Verify that IIS is set up to run ASP programs.
   1. Navigate to Windows Control Panel > Programs and Features > Turn Windows features on or off.
   2. Navigate to Internet Services > World Wide Web Services > Application Development Features.
   3. Verify that .NET Extensibility, ASP, ASP.NET, ISAPI Extensions, and ISAPI Filters are checked.
6. If .Net was installed on the server before IIS was enabled, IIS may not be able to run ASP.Net programs.
     Using the Windows command prompt, type:

cd C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727
aspnet_regiis –ir

Reference: 
Troubleshooting an ASP.NET Installation (IIS 6.0)

7. Test the ArcGIS Online Group ID and token using the URL below, replacing <GROUP_ID> and <TOKEN> with the appropriate values. The response in the browser will be an unformatted JSON structure.

http://localgovtemplates2.esri.com/MapsAndApps/proxy.ashx?http:
//www.arcgis.com/sharing/search?q=group:<GROUP_ID>&token=
<TOKEN>&start=0#=200&f=json

8. Repeat step 7 replacing the portion 'http://localgovtemplates2.esri.com/MapsAndApps' with the URL of the target Maps and Apps site. The response in the browser should be the same JSON structure as in step 7.