Automated Cloud update results in reboot loop. 
Manual installation of the latest installer also goes into a reboot loop after installing core services.
Installation completes install of 
Citrix Cloud Services Agent Logger
Citrix Cloud Services Agent System
Citrix Cloud Services Agent Watchdog

While components are being installed the system prompts for a reboot. 
Once the connector server reboots it then goes through the process again causing a loop. 

Installation Logs show:
MSI (s) (D0:B4) [18:00:13:297]: Executing op: CustomActionSchedule(Action=CA_RunHighAvailabilityPIPC,ActionType=3073,Source=BinaryData,Target=CAQuietExec64,CustomActionData="C:\Windows\System32\WindowsPowerShell\v1.0\PowerShell.exe" -ExecutionPolicy Unrestricted -NonInteractive -Command & "\"C:\Program Files\Citrix\Broker\Service\Setup Scripts\ConfigureHighAvailabilityService.ps1\"")
MSI (s) (D0:1C) [18:00:13:300]: Invoking remote custom action. DLL: C:\Windows\Installer\MSIC388.tmp, Entrypoint: CAQuietExec64
CAQuietExec64:  & : File C:\Program Files\Citrix\Broker\Service\Setup Scripts\ConfigureHighAvailabilityService.ps1 cannot be loaded 
CAQuietExec64:  because running scripts is disabled on this system. For more information, see about_Execution_Policies at 
CAQuietExec64:  https:/go.microsoft.com/fwlink/?LinkID=135170.
CAQuietExec64:  At line:1 char:3
CAQuietExec64:  + & "C:\Program Files\Citrix\Broker\Service\Setup Scripts\ConfigureHigh ...
CAQuietExec64:  +   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
CAQuietExec64:      + CategoryInfo          : SecurityError: (:) , PSSecurityException
CAQuietExec64:      + FullyQualifiedErrorId : UnauthorizedAccess
CAQuietExec64:  Error 0x80070001: Command line returned an error.
CAQuietExec64:  Error 0x80070001: QuietExec64 Failed
CAQuietExec64:  Error 0x80070001: Failed in ExecCommon64 method
CustomAction CA_RunHighAvailabilityPIPC returned actual error code 1603

Collect installation logs" 
Events that occurred during installation are available in the Windows Event Viewer. You can also review Cloud Connector installation logs, which are located at %LOCALAPPDATA%\Temp\CitrixLogs\CloudServicesSetup. Logs are also added to %ProgramData%\Citrix\WorkspaceCloud\InstallLogs after installation. 
https://docs.citrix.com/en-us/citrix-cloud/citrix-cloud-resource-locations/citrix-cloud-connector/installation.html#installation-logs

Review logs for errors. Found 1603 for powershell being blocked scripts are disabled.  
Remove GPO Policy  that has disabled scripts. 
Or Move Machine to Block inheritance OU to remove policies.  

Run Get-ExecutionPolicy to verify that powershell is set to "RemoteSigned" or "Unrestricted"
Remove Failed installation from Connector Server and reboot.
Reinstall Cloud Connecter Software. 

Note: Re-applying of blocking policies after successful installation may result in future update failures.

Problem Cause

PowerShell installation scripts being blocked by Policy or AV

Cloud connector is not connecting - failing update or install - reboot loop.