Could not download PDF from base 64 data from web service . Why?

Friends,
I got a web service output as base 64 encoded data for PDF. I response i get the value , but no pdf output…

My Web service provider method is

getOwnershipCertificate(lb,bid,reason)
  {
    var obj = {wspassword: 'Ikm#itmi$$i0n', wsname: 'getOwnershipCertPDF', lb: lb, bid: bid, reason: reason  };
    var myData = JSON.stringify(obj);
    if(this.data)
    {
      return Promise.resolve(this.data);
    } else {
      return new Promise 
      (
        (resolve,reject) => 
                    {
                      this.http.post('http://ccc.jhj.gov.in/mobservice/index.php/sanchaya/',myData,{ headers: new HttpHeaders()
                      , responseType: 'json'})
                      //.map(res => res)
                      .subscribe
                                 (res => {
                                    resolve(res);
                                   },
                                   err => {console.log("oops some error on taking ownership certificate PDF base 64 encoded string");reject(err);}
                                 );
                    }
      );
    }
  }

My Controller functions are

getOwnershipCertificate(lb, bid, reason) {
    this.certificateProvider.getOwnershipCertificate(lb, bid, reason)
    .then(data => {
        let downloadPDF: any = data[0].ownershippdf;
        //let base64pdf = 'data:application/pdf;base64,' + downloadPDF;
        let base64pdf = downloadPDF;
        console.log("log is"+base64pdf);
        let blobPdf = this.b64toBlob(base64pdf, 'application/pdf',512);
 
        this.file.writeFile(this.file.externalRootDirectory, 'Ownership.pdf', blobPdf, { replace: true })
     .then(res => {
           console.log('wres', res);
         this.fileOpener.open(res.toInternalURL(), 'application/pdf').then((ores) => {
               console.log('ores', ores)
         }).catch(err => {
             console.log('open error');
         });
     }).catch(err => {
         console.log('save error');
     });
    }).catch(err => {
        console.error('ownership get error',err);
    });
 }

and

b64toBlob(b64Data, contentType, sliceSize) {
    contentType = contentType || '';
    sliceSize = sliceSize || 512;
 
    let byteCharacters = atob(b64Data);
    let byteArrays = [];
 
    for (let offset = 0; offset < byteCharacters.length; offset += sliceSize) {
        let slice = byteCharacters.slice(offset, offset + sliceSize);
 
        let byteNumbers = new Array(slice.length);
 
        for (let i = 0; i < slice.length; i++) {
            byteNumbers[i] = slice.charCodeAt(i);
        }
 
        let byteArray = new Uint8Array(byteNumbers);
 
        byteArrays.push(byteArray);
    }
 
    var blob = new Blob(byteArrays, {type: contentType});
    return blob;
 }

My sample base 64 output is : Sample pdf base 64 value

I did not any error and got the base 64 encoded data as output. Please advise how to download pdf and open it default…

Thanks

Anes