"Bad Request" when downloading lib with Linux client


I’m using Seafile Server 7.0.4 on my Ubuntu-Linux server. It’s up and running without problems.
I can browse my libs with the web client. The Windows client is working as well.
Now I wanted to install the Linux client, but I cannot download any data from the server. I keep getting a “Bad Request” error:

$seaf-cli init -d ~/seafile-client/
$seaf-cli start
$seaf-cli status
# Name                                                  Status                  Progress
$seaf-cli download -l 9e47b0c9-20e6-4222-8b5a-cd5914ec1760 -s -d my_dir -u my_id -p my_password
Traceback (most recent call last):
File "/usr/bin/seaf-cli", line 998, in <module>
File "/usr/bin/seaf-cli", line 994, in main
File "/usr/bin/seaf-cli", line 658, in seaf_sync
token = get_token(url, username, password, tfa, conf_dir)
File "/usr/bin/seaf-cli", line 308, in get_token
token_json = urlopen("%s/api2/auth-token/" % url, data=data, headers=headers)
File "/usr/bin/seaf-cli", line 241, in urlopen
resp = urllib.request.urlopen(req)
File "/usr/lib/python2.7/dist-packages/future/backports/urllib/request.py", line 171, in urlopen
return opener.open(url, data, timeout)
File "/usr/lib/python2.7/dist-packages/future/backports/urllib/request.py", line 500, in open
response = meth(req, response)
File "/usr/lib/python2.7/dist-packages/future/backports/urllib/request.py", line 612, in http_response
'http', request, response, code, msg, hdrs)
File "/usr/lib/python2.7/dist-packages/future/backports/urllib/request.py", line 538, in error
return self._call_chain(*args)
File "/usr/lib/python2.7/dist-packages/future/backports/urllib/request.py", line 466, in _call_chain
result = func(*args)
File "/usr/lib/python2.7/dist-packages/future/backports/urllib/request.py", line 620, in http_error_default
raise HTTPError(req.full_url, code, msg, hdrs, fp) future.backports.urllib.error.HTTPError: HTTP Error 400: Bad Request

What can I do to solve this problem?