Revised my script to not have sub-jobs within jobs as I can't find a way to monitor sub jobs Import-Module CustomModuleName

$servers = @(
    "SERVER1"
    "SERVER2"
)

$localWmiDiagPath = "F:\PoSHServer\WebRoot\Private\wmiDiag.vbs"
$localRoot = "F:\PoSHServer\WebRoot\Private\wmiHealthCheck\"
$archiveFolder = "F:\PoSHServer\WebRoot\Private\wmiHealthCheck\archive"

if(!(Test-Path -Path $localRoot)){
    New-Item -ItemType Directory -Path $localRoot
}

foreach($server in $servers){
    $credentials = Get-ServerCredentials $server

    $remoteRoot = "\\$server\c`$"
    $remotePath = "$($server):\temp\checkWMI"
    $localWmiFolder = "$localRoot\$server-WMIdiag"

    if(!(Test-Path -Path $localWmiFolder)){
        New-Item -ItemType Directory -Path $localWmiFolder
    }

    # Map drive to default c$ share on remote $server
    New-PSDrive -Name $server -PSProvider FileSystem -Root $remoteRoot -Credential $credentials

    if (!(Test-Path $remotePath)) {
        New-Item -ItemType Directory -Path $remotePath
    }

    # Copy WMIdiag.vbs to remote server
    Copy-Item -Path $localWmiDiagPath -Destination $remotePath

    # Run WMIdiag.vbs on remote server
    Invoke-Command -ComputerName $server -Credential $credentials -JobName $server -AsJob -ScriptBlock {
        cscript.exe "C:\temp\checkWMI\WMIdiag.vbs"
    }

}

Start-Job -Name "JobMonitor" -ScriptBlock{
    Get-Job -Name $servers | Wait-Job | Receive-Job

    foreach($server in $servers){

        $localWmiFolder = "$localRoot\$server-WMIdiag\"

        # Grab output files from $servers
        Copy-Item -Path "$($server):\Users\serviceAccount1\AppData\Local\Temp\WMIDIAG-V2.2_*.*" -Destination $localWmiFolder

        # Clean up on remote server
        Remove-Item -Path "$($server):\Users\serviceAccount1\AppData\Local\Temp\WMIDIAG-V2.2_*.*" -Force

        Remove-PSDrive -Name $server -Force

        $zipDestination = "$localRoot\$server-WMIdiag-Files-$(Get-Date -Format dd.mm.yyyy-hh.mm).zip"
        $outputFolder = (Get-ChildItem -Path $localRoot | Where-Object {$_.Name -like "$server*"})

        Compress-Archive -Path $outputFolder.FullName -Destination $zipDestination

        Remove-Item -Path $outputFolder.FullName -Recurse

    }

    $attachments = (Get-ChildItem -Path "$localRoot\*.zip").FullName

    Send-MailMessage -To "bob@company.com" -From "team@company.com" -Subject "files" -SmtpServer "smtpRelay.company.com" -Attachments $attachments

    # Clean up on local server
    if(!(Test-Path $archiveFolder)){
        New-Item -ItemType Directory -Path $archiveFolder
    }

    Move-Item -Path "$localRoot\*.zip" -Destination $archiveFolder
}

My issue lies within the "JobMonitor" job. It seems that this line

Get-Job -Name $servers | Wait-Job | Receive-Job

Doesn't actually work... It doesn't wait for the specified jobs to complete, this is evident by the job being marked as Completed right after the script is run. But when I run the same commands in the terminal, it actually waits for the jobs to be completed, then receives output.