Create Document Task : Flow action generates document task but gives attachment not found error all

[Kachu]

All the time when  i try create Document task in flow designer it generates the document task but  when i try to fill document it says attachment is missing. does any one know how to resolve this issue ?

[Kachu]

Iam using PDf template and my document templates are published, when i create them usingsc ript includ using Below script 

 var docApi = new sn_doc.GenerateDocumentAPI();

            var docTaskId = docApi.initiateDocumentTasks(

                incidentGr, // taskGr: parent record for the doc task

                htmlBody, // html body (empty to use template)

                template_type, // template sys_id

                generatedPdfName, // output file name

                incidentGr.getUniqueValue() // documentId (tie to incident)

            );
it creates as expected but when it resturns true or false not record sysid  adn creates async'ly . I need to create  and get me back sysid. I do glide it doesnot work  because of async, i want to use flow action to generate but then again attachment not found issue comes up.