Base 64 pdf not downloaded in lolipop 5.1.1 . Why?

Friends,

I am using file,fleopener plugins to create and open a pdf file , the data came as base64.

My Relevant code is below . There is no Error shown in console and no PDF created…

  getOwnershipCertificate(lb, bid, reason) {
    if(this.global1.getnetwork())
    {  
        this.connectivityFlag = true;
        this.certificateProvider.getOwnershipCertificate(lb, bid, reason)
        .then(data => {
            var downloadPDF: any = data[0].ownershippdf;
            var base64pdf = downloadPDF;
            var contentType = 'application/pdf';
            const writeDirectory = this.platform.is('ios') ? this.file.dataDirectory : this.file.externalDataDirectory;
            var fileName = "Ownership.pdf";
            this.file.writeFile(writeDirectory, fileName, this.convertBaseb64ToBlob(downloadPDF, 'data:application/pdf;base64'), {replace: true})
    .then(() => {

        this.fileOpener.open(writeDirectory + fileName, 'application/pdf')
            .catch(() => {
                console.log('Error opening pdf file');
            });
    })
    .catch(() => {
        console.error('Error writing pdf file');

    });


    }).catch(err => {
        console.error('ownership get error',err);

    }); 

   } else {
    alert("You are offline, please be online to get ownership certificate");
   }
 }

blob creating function

 convertBaseb64ToBlob(b64Data, contentType): Blob {
  contentType = contentType || '';
  const sliceSize = 512;
  b64Data = b64Data.replace(/^[^,]+,/, '');
  b64Data = b64Data.replace(/\s/g, '');
  const byteCharacters = window.atob(b64Data);
  const byteArrays = [];
  for (let offset = 0; offset < byteCharacters.length; offset += sliceSize) {
       const slice = byteCharacters.slice(offset, offset + sliceSize);
       const byteNumbers = new Array(slice.length);
       for (let i = 0; i < slice.length; i++) {
           byteNumbers[i] = slice.charCodeAt(i);
       }
       const byteArray = new Uint8Array(byteNumbers);
       byteArrays.push(byteArray);
  }
 return new Blob(byteArrays, {type: contentType});
}

Waiting a Fast reply. I am struggling this for 33 days now…

Thanks

Anes