Error Message :
Invalid credentials, reason: 'Global UC4 error' (1004)
U02000099 Transfer key could not be loaded (Ret='458752', minor='1004'). Please check, if the KeyStore exists and the agent is authenticated.

The Windows Agent loops at start up, if there is no transfer key, but the Agent is already “authenticated” within the Automation Engine.
 
Example:
Here an example which depicts the issue in detail and also the steps to reproduce:

• Agent “VWGSUP12” is already Authenticated within the Automation Engine. This can be looked-up in Administration Perspective at Agents:

• There is no keystore file or an empty keystore file during the Agent installation. (Default, no UCXJWX6.kstr in the bin directory):
  
  

  

  
  
   
• After the Agent starts the following error is reported in the Agent’s log file:
  
  Invalid credentials, reason: 'Global UC4 error' (1004)
  U02000099 Transfer key could not be loaded (Ret='458752', minor='1004'). Please check, if the KeyStore exists and the agent is authenticated.
   
• This is OK so far, because the Agent is Authenticated, so it needs to already have a key.
   
• Unfortunately the Agent tries to connect in an infinite loop – and gets the same error each time. In this situation the Agent consumes a lot of CPU (typically one core) and the log (and trace) file grows rapidly:
  
  20170925/082505.702 - U02000072 Connection to system 'WO121' initiated.
  20170925/082505.703 - U02000011 Connection to Server '192.168.0.49(VWGSUP12):14219' initiated.
  20170925/082505.711 - U02000004 Connection to Server 'WO121#CP003' successfully created.
  20170925/082505.711 - U02000354 CP Server 'WO121#CP003' reports ranking '1'.
  20170925/082505.712 - U02000073 Connection to system 'WO121' via CP Server 'WO121#CP003' successfully established.
  20170925/082505.747 -           Invalid credentials, reason: 'Global UC4 error' (1004)
  20170925/082505.747 - U02000099 Transfer key could not be loaded (Ret='458752', minor='1004').  Please check, if the KeyStore exists and the agent is authenticated.
  20170925/082505.747 - U02000010 Connection to Server 'WO121#CP003' terminated.
  20170925/082505.752 - U02000072 Connection to system 'WO121' initiated.
  20170925/082505.753 - U02000011 Connection to Server '192.168.0.49(vwgsup12):14217' initiated.
  20170925/082505.778 - U02000004 Connection to Server 'WO121#CP001' successfully created.
  20170925/082505.778 - U02000354 CP Server 'WO121#CP001' reports ranking '1'.
  20170925/082505.778 - U02000073 Connection to system 'WO121' via CP Server 'WO121#CP001' successfully established.
  20170925/082505.784 -           Invalid credentials, reason: 'Global UC4 error' (1004)
  20170925/082505.784 - U02000099 Transfer key could not be loaded (Ret='458752', minor='1004').  Please check, if the KeyStore exists and the agent is authenticated.
  20170925/082505.784 - U02000010 Connection to Server 'WO121#CP001' terminated.

Expected behavior:

• The Agent should terminate after the first attempt. The keystore file or key will not appear somehow so looping makes no sense.
   
• At least there should be some waiting time between the attempts, e.g. connect time.