Kentico Media Upload "The system cannot find the file specified"

We have Kentico configured to use AWS for storing files in the media library, but when we go to upload a file to the media library it makes it to 100% and throws the error "The system cannot find the file specified".

The event log isn't much help with this as the detail of the error: "Message: The system cannot find the file specified

Exception type: System.ComponentModel.Win32Exception
Stack trace:
at System.Diagnostics.Process.StartWithCreateProcess(ProcessStartInfo startInfo)
at Dianoga.Optimizers.CommandLineToolOptimizer.ExecuteProcess(String arguments)
at Dianoga.Optimizers.CommandLineToolOptimizer.ProcessOptimizer(OptimizerArgs args)
at Dianoga.Optimizers.OptimizerProcessor.Process(OptimizerArgs args)
at Dianoga.Jpeg.JpegOptimizer.ProcessStream(Byte[] imageBytes)
at Dianoga.Jpeg.JpegOptimizer.Optimize(MediaFileInfo file)
at Dianoga.MediaOptimizer.Process(MediaFileInfo stream)
at Dianoga.MediaOptimizer.MediaFile_Insert_Before(Object sender, ObjectEventArgs e)
at CMS.Base.AbstractHandler.CallEventHandler[TArgs](EventHandler`1 h, TArgs e)
at CMS.Base.AbstractHandler.Raise[TArgs](String partName, List`1 list, TArgs e, Boolean important)
at CMS.Base.AdvancedHandler`2.RaiseBefore(TArgs e)
at CMS.Base.AdvancedHandler`2.RaiseBefore(TArgs e)
at CMS.Base.AdvancedHandler`2.StartEvent(TArgs e, Boolean allowEvent)
at CMS.DataEngine.ObjectHandler.StartEvent(BaseInfo obj)
at CMS.DataEngine.AbstractInfoBase`1.InsertData()
at CMS.DataEngine.AbstractInfoProvider`3.SetInfo(TInfo info)
at CMS.MediaLibrary.MediaFileInfoProvider.SetMediaFileInfoInternal(MediaFileInfo mediaFile, Boolean saveFileToDisk, Int32 userId, Boolean ensureUniqueFileName)
at CMS.MediaLibrary.Web.UI.MediaLibraryUploader.HandleMediaLibraryUpload(UploaderHelper args, HttpContext context)"

Does anyone know what the actual problem may be or how to resolve it?