Getting "Failed to run action: RegisterExternalAgents" while trying to install or upgrade the Symantec Management Agent

Products

• IT Management Suite

Issue/Introduction

Symantec Management Agent (aka SMA or Altiris Agent) fails to upgrade on Client Machines.
In some instances the base Altiris Agent is installed but the Agent UI is missing tabs (like Package Server, Task Status, etc) or it doesn't open or subcomponents (like Altiris Base Task Handlers) are missing.

From Agent Install Logs (under C:\ProgramData\Symantec\Symantec Agent\Logs):

2015-06-24 11:35:13: + Running action: CopyAgentFilesTree
2015-06-24 11:35:13: + Running action: InstallCoreAgentDll
2015-06-24 11:35:14: + Running action: InstallCommonDll
2015-06-24 11:35:15: + Running action: InstallSupportDll
2015-06-24 11:35:15: + Running action: InstallCoreAgentExe
2015-06-24 11:35:15: Registering Core Agent service...
2015-06-24 11:35:15: Registered AeXNSAgent.exe
2015-06-24 11:35:15: + Running action: InstallSurrogatesForX86
2015-06-24 11:35:15: Registering 32-bit host surrogate app (AeXNSAgentHostSurrogate32.exe)...
2015-06-24 11:35:15: Registering 32-bit UI surrogate app (AeXAgentUIHostSurrogate32.exe)..
2015-06-24 11:35:15: + Running action: InstallOutprocHosters
2015-06-24 11:35:15: + Running action: RegisterExternalAgents
2015-06-24 11:35:18: Upgrade failed. Error message: Failed to run action: RegisterExternalAgents
2015-06-24 11:35:18: Core Agent Re-Installation Ended 
2015-06-24 11:35:18: ==================================
2015-06-24 11:35:18: Core Agent Installation Ended 
2015-06-24 11:35:18: ===============================

Environment

ITMS 7.x, 8.x

Cause

"Application Experience" service was disabled.

Resolution

1. Open Windows Services and look for "Application Experience" service (AeLookupSvc). It is usually set by default to "Manual" Startup type. Make sure it is started.
2. After this Microsoft Service is running again, you can try to push or pull the Altiris Agent again
   Note:  If the Altiris Agent is already partially present on the machine, you can run directly  AeXNSC.exe /reinstall path="C:\Program Files\Altiris\Altiris Agent" in order to get the missing parts reinstalled.