Event Viewer:
Citrix ConfigSync Service event ID 505:  The Citrix Config Sync Service failed an import.
Error details:
Error importing configuration data into secondary Broker.
Net-BrokerImportDb: Unknown error occurred
Exception Position: ConfigSync.ps1:1607

CDF Traces:
HighAvailabilityService.exe,0,BrokerSDKLogic,,0,,1,Error,"HA::HighAvailabilitySDKLogic.CreateDatabase caught: System.Data.SqlClient.SqlException (0x80131904): **** ERROR **** : Citrix Broker Service: Schema creation requires SQL Server 2016 or later.

1. If you don't have the .ISO for 2203 saved, download a copy from https://www.citrix.com/downloads/citrix-virtual-apps-and-desktops/
2. Mount the 2203 LTSR ISO to the DDC
3. Stop the Citrix High Availability Service on the DDC
4. Navigate to Programs and Features in the Control Panel, or enter appwiz.cpl from the system's Run dialog (accessible with the keyboard shortcut Win+R)
5. Select the program Microsoft SQL Server 2014 Express LocalDB and uninstall it
6. From the mounted 2203 ISO, navigate to Support/SQLLocalDB and launch SqlLocalDB.exe
7. Complete the installation steps on-screen
8. Start the HA service on the DDC

Problem Cause

DDC 2203 is not compatible with versions of SQL Server Express prior to 2016, but version 7.15 installs SQL Server Express 2014. Citrix does not upgrade SQL Server Express installations automatically in case the customer has other components that rely upon it.