$myVars = '$(armDeploymentOutput)' | ConvertFrom-Json
Write-Host "The following variables are available: $($myVars)" -Verbose
$existingVaultName = $myVars.existingKeyVaultName.value
$webappName=$myVars.webappName.value
$webAppCustomHostname=$myVars.webAppCustomHostname.value
$certName=$myVars.existingKeyVaultCertificateName.value

if ($webappName -and $webAppCustomHostname -and $existingVaultName -and $certName) {
    Write-Host "Attempting to enable SSL Binding for $($webappName) on the hostname $($webAppCustomHostname) using cert $($certName) from the existing keyvault of $($existingVaultName)." -Verbose
    Enable-SslStateOnWebapp -WebappName $webappName -customWebappHostname $webAppCustomHostname -existingKeyvaultName $existingVaultName -existingKeyvaultCertName $certName
}
else {
    Write-Host "Insufficient parameters have been provided to complete SSL Binding. To enable SSL binding, please provide a custom hostname, an existing keyvault where your certificate is stored, and the name of your certificate. Please visit the readme for more information." -Verbose
}

function Enable-SslStateOnWebapp {
    param (
        [Parameter(
            Mandatory = $true,
            HelpMessage = 'A webapp name is required.')]
        [ValidateNotNullOrEmpty()]
        [string] $WebappName,

        [PARAMETER(
            Mandatory = $true,
            HelpMessage = 'The FQDN of the custom hostname you want to bind.')]
        [ValidateNotNullOrEmpty()]
        [string] $customWebappHostname,

        [Parameter(
            Mandatory = $true,
            HelpMessage = 'A name for an existing Keyvault is required.')]
        [ValidateNotNullOrEmpty()]
        [string] $existingKeyvaultName,

        [PARAMETER(
            Mandatory = $true,
            HelpMessage = 'A name of the pfx certificate stored in the pre-existing keyvault')]
        [ValidateNotNullOrEmpty()]
        [string] $existingKeyVaultCertName
    )
    #getting webapp resources
    $webapp = Get-AzureRmResource -Name $webappName
    #obtaining resource group resources through the use of resource group name tied to webapp
    $rg = Get-AzureRmResource -ResourceGroupName $webapp.ResourceGroupName

...

}

2019-07-16T23:00:39.1496157Z ##[debug]Caught exception from task script.
2019-07-16T23:00:39.1536232Z ##[debug]Error record:
2019-07-16T23:00:39.1993172Z ##[debug]Enable-SslStateOnWebapp : Parameter set cannot be resolved using the specified named parameters.
2019-07-16T23:00:40.2927954Z ##[debug]At D:agent3_work_temp7be280f0-5905-4e05-99e0-972c90739a12.ps1:13 char:5
2019-07-16T23:00:40.2930113Z ##[debug]+     Enable-SslStateOnWebapp -WebappName $webappName -customWebappHost ...
2019-07-16T23:00:40.2940404Z ##[debug]+     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2019-07-16T23:00:40.2940886Z ##[debug]    + CategoryInfo          : InvalidArgument: (:) [Enable-SslStateOnWebapp],     ParameterBindingException
2019-07-16T23:00:40.2941287Z ##[debug]    + FullyQualifiedErrorId : AmbiguousParameterSet,Enable-SslStateOnWebapp
2019-07-16T23:00:40.2941647Z ##[debug]
2019-07-16T23:00:40.2941968Z ##[debug]Script stack trace:
2019-07-16T23:00:40.2942368Z ##[debug]at Enable-SslStateOnWebapp, D:agent3_workr6a_infra-grs-referenceappdroppwsh-modulesgrs-armenable-ssl_state_on_webappenable-ssl_state_on_webapp.ps1: line 64