In one project function for create pdf and download not work in another place. Why?

Dear Friends,

in one of my sample code the function works for creation and download of PDF as follows

createPdf(epayTransID,status,ReceiptDate,TaxPeriod,TotAmount,BankRefNo) {

   var docDefinition = {
     content: [
       { text: 'Payment Receipt', style: 'header' },
       { text: new Date().toTimeString(), alignment: 'right' },

       { text: 'Transaction ID', style: 'subheader' },
       { text: epayTransID },

       { text: 'Status', style: 'subheader' },
       { text: status },


       { text: 'Receipt Date', style: 'subheader'},
       { text: ReceiptDate },

       { text: 'Tax Period', style: 'subheader'},
       { text: TaxPeriod },

       { text: 'Total Amount', style: 'subheader'},
       { text: TotAmount},

       { text: 'Bank Reference no', style: 'subheader'},
       { text: BankRefNo},
       
     ],
     styles: {
       header: {
         fontSize: 18,
         bold: true,
       },
       subheader: {
         fontSize: 14,
         bold: true,
         margin: [0, 15, 0, 0]
       },
       story: {
         italic: true,
         alignment: 'center',
         width: '50%',
       }
     }
   }
   this.pdfObj = pdfMake.createPdf(docDefinition).getBlob(buffer => {
     this.file.resolveDirectoryUrl(this.file.externalRootDirectory)
       .then(dirEntry => {
         this.file.getFile(dirEntry, 'paymentreceipt.pdf', { create: true })
           .then(fileEntry => {
             fileEntry.createWriter(writer => {
               writer.onwrite = () => {
                 this.fileOpener.open(fileEntry.toURL(), 'application/pdf')
                   .then(res => { })
                   .catch(err => {
                   });
               }
               writer.write(buffer);
             })
           })
           .catch(err => {
             //const alert = this.alertCtrl.create({ message: err, buttons: ['Ok'] });
             //alert.present();
           });
       })
       .catch(err => {
         //const alert = this.alertCtrl.create({ message: err, buttons: ['Ok'] });
         //alert.present();
       });

   });
 }

but in another project place it will not work without any error
please any body help … I am looking this for 3 days :d

Thanks

Anes