Run cmdlet with debugging options

Enable powershell debugging

$global:VerbosePreference = 'Continue'
$global:DebugPreference = 'Continue'
Start-Transcript -Path .\Output.log
New-VeeamDiagram -Target backupserver -Username "domain\username" -Password password -Format png -Direction top-to-bottom -OutputFolderPath C:\Users\username\ -DiagramType Diagram-Type -EnableErrorDebug <-- your command here
Stop-Transcript-EnableErrorDebug

After saving the report, reset powershell to default settings

$global:VerbosePreference = 'SilentlyContinue'
$global:DebugPreference = 'SilentlyContinue'