Why doesn't this automation work?

I have written an automation in Velocity to remind users when they have reached their quota for images and redirect them to a page, but it doesn't work. The event that I have selected to trigger the automation is Media.BeforeCreate. Here's the code:

#set($user = false)
#set($user = $core_v2_user.Accessing)

#set($imageQuota = $core_v2_utility.ParseInt($user.ExtendedAttributes.get_Item("ImageQuota").Value))

#set($imageList = $core_v2_media.List("%{ AuthorId=$user.Id, IncludeUnpublished='True' }"))
#set($imageCount = $imageList.Count)

#if ($imageCount >= $imageQuota)
 {"redirectUrl":"$core_v2_encoding.JavascriptEncode($core_v2_urls.Custom('Select_Plan'))","message":"$core_v2_encoding.JavascriptEncode($core_v2_language.FormatString($core_v2_language.GetResource('ImageQuotaReached'), $core_v2_language.FormatNumber($imageCount), $core_v2_language.FormatNumber($imageQuota)))"}
#end