Error when muting alarms via powershell?

Making a script that will accept user input so they can pick a "Schedule from" and "schedule to" date.

Then I want to pass that to SuppressAlerts. 

I keep getting "Invoke-SwisVerb : Verb Orion.AlertSuppression.SuppressAlerts cannot unpackage parameter 0 of type System.String[]"

$global:TimePicker = $TimePicker.Text
    $global:datePicker = $datePicker.Text
    $global:ToTimePicker = $ToTimePicker.Text
    $global:TodatePicker = $TodatePicker.Text 
}
scheduleForm
[string]$datePicker = (Get-Date "$datePicker $TimePicker")::UtcNow
[string]$TodatePicker = (Get-date "$TodatePicker $ToTimePicker")::UtcNow

foreach($server in get-content -path $ServerList){
    $nodeUri = Get-SwisData $swis "SELECT Uri FROM Orion.nodes WHERE caption=`'$server`'"
    $nodeUri = $nodeUri |% {[string]$_}
    Invoke-SwisVerb $swis Orion.AlertSuppression SuppressAlerts @($nodeUri, $datePicker, $TodatePicker) | Out-Null
#    Invoke-SwisVerb $swis Orion.AlertSuppression SuppressAlerts @($nodeID, $datePicker, $TodatePicker, $false) | Out-Null
}