Download link format: https://msdownloadcdn.azureedge.net/files/XProtect%20{YEAR}%20{RELEASE}/Software/Advanced%20VMS/Milestone%20XProtect%20VMS%20Products%20{YEAR}%20{RELEASE}%20System%20Installer.exe.
Replace {YEAR} with the year, e.g. 2023, and {RELEASE} with the release, e.g. R2.
The service account should be CCTV\Administrator. You can double check in services.msc (all the Milestone services' “Log On As” column).