Python _ctypes.COMError: -2146827284 (comtypes模块) on IIS web server

我把我的python flask API放在一个虚拟机上，我使用IIS webserver。当我从我的前端发送请求时，文件被上传，但转换失败。(如果我尝试在localhost上做，则工作正常）。有什么办法可以解决吗？

服务器，上传路线。

@app.route("/upload", methods=["POST"])
def upload():
    file = request.files['file']
    id = request.form['id']
    uid = request.form['uid']
    tool = request.form['tool']
    Path(f"./uploads/{id}").mkdir(parents=True, exist_ok=True) 
    extension = os.path.splitext(file.filename)[1]
    file.save(f"./uploads/{id}/{uid}{extension}")
    if tool == "/jpg-to-pdf":
        img_to_pdf(f"./uploads/{id}/{uid}{extension}", id)
    elif tool == "/excel-to-pdf":
        excel_to_pdf(f"./uploads/{id}/{uid}{extension}")
Conversion script:
import comtypes.client
import pythoncom
import os
def excel_to_pdf(file):
    pythoncom.CoInitialize()
    out_file = os.path.splitext(os.path.abspath(file))[0] + '.pdf'
    in_file = os.path.abspath(file)
    print(in_file)
    excel = comtypes.client.CreateObject('Excel.Application')
    excel.Visible = False
    doc = excel.Workbooks.Open(in_file)
    doc.ExportAsFixedFormat(0, out_file, 1, 0)
    doc.Close()
    excel.Quit()
Error:
Exception on /upload [POST]
Traceback (most recent call last):
  File "C:\Users\Deschizatorul\AppData\Local\Programs\Python\Python310\lib\site-packages\flask\app.py", line 2525, in wsgi_app
    response = self.full_dispatch_request()
  File "C:\Users\Deschizatorul\AppData\Local\Programs\Python\Python310\lib\site-packages\flask\app.py", line 1822, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "C:\Users\Deschizatorul\AppData\Local\Programs\Python\Python310\lib\site-packages\flask_cors\extension.py", line 165, in wrapped_function
    return cors_after_request(app.make_response(f(*args, **kwargs)))
  File "C:\Users\Deschizatorul\AppData\Local\Programs\Python\Python310\lib\site-packages\flask\app.py", line 1820, in full_dispatch_request
    rv = self.dispatch_request()
  File "C:\Users\Deschizatorul\AppData\Local\Programs\Python\Python310\lib\site-packages\flask\app.py", line 1796, in dispatch_request
    return self.ensure_sync(self.view_functions[rule.endpoint])(**view_args)
  File "C:\inetpub\wwwroot\flask-server\.\server.py", line 63, in upload