Error in Downloading Files from Django app in Production with Gunicorn & Nginx

Question

I have deployed my Django app on AWS EC2 Instance using this guide.

Everything is working fine but the error arises when I download an excel file. (Excel is created using opnenpyxl library).

While downloading an xlsx file the application is returning download.htm file. Everything work great on a development server.

I tried

1. Adding and removing the download tag. <a href="{% url 'download_estimate_excel_file' project.id project.name %}" class="dropdown-item" download> Download Excel </a>. [Didn't Work]
2. Adding [service] Environment="LANG=ru_RU.UTF-8" to gunicorn.service file (found this on StackOverflow also). [Didn't Work]

EDIT:

Path for Gunicorn config: /etc/systemd/system/gunicorn.service

>> GUNICRON CONFIG

[Unit]
Description=gunicorn daemon
Requires=gunicorn.socket
After=network.target

[Service]
User=sammy
Group=www-data
WorkingDirectory=/home/sammy/myprojectdir
ExecStart=/home/sammy/myprojectdir/myprojectenv/bin/gunicorn \
          --access-logfile - \
          --workers 3 \
          --bind unix:/run/gunicorn.sock \
          myproject.wsgi:application
Environment="LANG=ru_RU.UTF-8"

[Install]
WantedBy=multi-user.target

Path for Nginx config: /etc/nginx/sites-available/<myproject>

>> NGINX CONFIG

server {
    listen 80;
    server_name server_domain_or_IP;

    location = /favicon.ico { access_log off; log_not_found off; }
    location /static/ {
        root /home/sammy/myprojectdir;
    }

    location / {
        include proxy_params;
        proxy_pass http://unix:/run/gunicorn.sock;
    }
}

>> download_estimate_excel_file function

@login_required
def download_estimate_excel_file(request, project_id, project_name):
    project_tnc_obj = ProjectTermsAndConditions.objects.filter(
        project=project_id)
    date_time_obj = datetime.now()
    current_date = date_time_obj.strftime('%x')
    current_time = date_time_obj.strftime('%X')

    filename = project_name + '_' + str(current_date).replace('/', "-") + '_' + str(current_time).replace(":", "-") + ".xlsx"

    file_path = "media/excel/" + filename

    ...
    ...

    sheet.append([""])

    workbook.save(filename=str(file_path))
    workbook.close()
    file_ecxel = FileResponse(open(file_path, 'rb'))
    delete_file = os.remove(file_path)
    return file_ecxel

>> UPDATED download_estimate_excel_file function

@login_required
def download_estimate_excel_file(request, project_id, project_name):
    project_tnc_obj = ProjectTermsAndConditions.objects.filter(
        project=project_id)
    date_time_obj = datetime.now()
    current_date = date_time_obj.strftime('%x')
    current_time = date_time_obj.strftime('%X')

    filename = project_name + '_' + str(current_date).replace('/', "-") + '_' + str(current_time).replace(":", "-") + ".xlsx"

    file_path = "media/excel/" + filename

    ...
    ...

    sheet.append([""])

    workbook.save(filename=str(file_path))
    workbook.close()

    with open(file_path, "rb") as excel:
        data = excel.read()
    delete_file = os.remove(file_path)

    return HttpResponse(data, headers={
        'Content-Type': 'application/vnd.ms-excel',
        'Content-Disposition': 'attachment; filename= "{}"'.format(
            filename),
    })

Thanks in advance.