I have problems using simple-cdd for developing own install-isos

Error-messages:
Traceback (most recent call last):
  File "/usr/bin/simple-cdd", line 686, in <module>
    scdd.build_mirror()
  File "/usr/bin/simple-cdd", line 290, in build_mirror
    self.run_tool("mirror", tool)
  File "/usr/bin/simple-cdd", line 387, in run_tool
    tool.run()
  File "/usr/lib/python3/dist-packages/simple_cdd/tools/mirror_download.py", line 105, in run
    _download(download_release_file, release_file)
  File "/usr/lib/python3/dist-packages/simple_cdd/tools/mirror_download.py", line 55, in _download
    request.urlretrieve(url, filename=output)
  File "/usr/lib/python3.9/urllib/request.py", line 239, in urlretrieve
    with contextlib.closing(urlopen(url, data)) as fp:
  File "/usr/lib/python3.9/urllib/request.py", line 214, in urlopen
    return opener.open(url, data, timeout)
  File "/usr/lib/python3.9/urllib/request.py", line 523, in open
    response = meth(req, response)
  File "/usr/lib/python3.9/urllib/request.py", line 632, in http_response
    response = self.parent.error(
  File "/usr/lib/python3.9/urllib/request.py", line 561, in error
    return self._call_chain(*args)
  File "/usr/lib/python3.9/urllib/request.py", line 494, in _call_chain
    result = func(*args)
  File "/usr/lib/python3.9/urllib/request.py", line 641, in http_error_default
    raise HTTPError(req.full_url, code, msg, hdrs, fp)
urllib.error.HTTPError: HTTP Error 404: Not Found

Any Ideas? In Debian it works!

Best Thomas