Application Catalog - Cannot Connect to the Application Server

Today there was a issue with the Application Catalog. When starting the Application Catalog from Software Center the following error was displayed: "Cannot Connect to the Application Server". Strange thing because it was working earlier fine.

Actions that I've done to investigate it:

• Uninstall both Application Catalog roles
• Check SMSPORTALWEBSetup.log and SMSAWEBSVCSetup.log in the Configuration Manager folder to track the uninstall progress
• Install both Application Catalog roles with defaults
• Run %windir%\Microsoft.NET\Framework64\v4.0.30319\aspnet_regiis.exe /-i –enable
• Solution from SithaYuvaraj

Looking on MS TechNet I found the following post: SCCM 2012 App Catalog Web Page Error

For me this did the trick:

• Adding SYSTEM and/or Local Service account permissions on the Windows\Temp folder

After that the Application Catalog is running fine again! This permissions are needed to let SYSTEM and/or Local Service write to the folder.

Update 29-2: As mentioned on SithaYuvaraj, If you have IPV6 enabled on the SCCM server you may run into this issue as well. Disabling it (or configure it again) resolves this issue!