I can't download files from the apk

This part of my code is to install files (in this case a pdf)

  public DescargarPDF(): void {
    if (this.DataAcc.AccVer == "Cosechadora Arriba con Motor John Deere") {
      this.PDFRoot = "/assets/manuales/SeinmexCosechaArriba.pdf"
    }
    this.toastMesanje();
    this.Manual.DescargarManual(this.PDFRoot)
      .subscribe(response => {
        /*let fileName = response.headers.get("ManualCosechadoraArribaJohnDeere.pdf")*/

        let blob: Blob = response.body as Blob;
        let a = document.createElement('a');
        a.download = "ManualCosechadoraArribaJohnDeere.pdf";
        a.href = window.URL.createObjectURL(blob);
        a.click();
      })
  }

I created a service to connect to the pdf

import { HttpClient } from '@angular/common/http';
import { Injectable } from '@angular/core';


@Injectable({
  providedIn: 'root'
})
export class DescargarService {

  constructor(
    private Http: HttpClient) { }

  public DescargarManual(Maquina:string) {
    return this.Http.get(Maquina,
      { observe: 'response', responseType: 'blob' })

  }
}

On the website the code works but in the apk it doesn’t download anything

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