Seafile won't start on RPi / nginx returns error 500

I am trying to setup seafile again after I had to format the SD card of my raspberry pi. Now I am encountering starting errors with it.
I can successfully login with a clean seafile/nginx setup but after the login it says “Error” where normally the libraries would be. The web console says internal server error (500).
So I checked nginx and it seems the seafile fileserver port 8082 is not used by any program. The seahub.log file reports:

2019-10-28 11:46:22,716 [ERROR] seahub.notifications.utils:200 update_notice_det                                                                             ail Error received: 511 Unknown service (In _start_service)
2019-10-28 11:46:23,439 [ERROR] django.request:135 handle_uncaught_exception Int                                                                             ernal Server Error: /api2/account/info/
Traceback (most recent call last):
File "/home/seafile/seafile-server-7.0.5/seahub/thirdpart/Django-1.11.16-py2.7                                                                             .egg/django/core/handlers/exception.py", line 41, in inner
    response = get_response(request)
File "/home/seafile/seafile-server-7.0.5/seahub/thirdpart/Django-1.11.16-py2.7                                                                             .egg/django/core/handlers/base.py", line 249, in _legacy_get_response
    response = self._get_response(request)
File "/home/seafile/seafile-server-7.0.5/seahub/thirdpart/Django-1.11.16-py2.7                                                                             .egg/django/core/handlers/base.py", line 187, in _get_response
    response = self.process_exception_by_middleware(e, request)
File "/home/seafile/seafile-server-7.0.5/seahub/thirdpart/Django-1.11.16-py2.7                                                                             .egg/django/core/handlers/base.py", line 185, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "/home/seafile/seafile-server-7.0.5/seahub/thirdpart/Django-1.11.16-py2.7                                                                             .egg/django/views/decorators/csrf.py", line 58, in wrapped_view
    return view_func(*args, **kwargs)
File "/home/seafile/seafile-server-7.0.5/seahub/thirdpart/Django-1.11.16-py2.7                                                                             .egg/django/views/generic/base.py", line 68, in view
    return self.dispatch(request, *args, **kwargs)
File "/home/seafile/seafile-server-7.0.5/seahub/seahub/api2/base.py", line 23,                                                                              in dispatch
    response = super(APIView, self).dispatch(*a, **kw)
File "/home/seafile/seafile-server-7.0.5/seahub/thirdpart/djangorestframework-                                                                             3.3.3-py2.7.egg/rest_framework/views.py", line 466, in dispatch
    response = self.handle_exception(exc)
File "/home/seafile/seafile-server-7.0.5/seahub/seahub/api2/base.py", line 20,                                                                              in handle_exception
    return super(APIView, self).handle_exception(exc)
File "/home/seafile/seafile-server-7.0.5/seahub/thirdpart/djangorestframework-                                                                             3.3.3-py2.7.egg/rest_framework/views.py", line 463, in dispatch
    response = handler(request, *args, **kwargs)
File "/home/seafile/seafile-server-7.0.5/seahub/seahub/api2/views.py", line 34                                                                             0, in get
    return Response(self._get_account_info(request))
File "/home/seafile/seafile-server-7.0.5/seahub/seahub/api2/views.py", line 31                                                                             1, in _get_account_info
    quota_total = seafile_api.get_user_quota(email)
File "/home/seafile/seafile-server-7.0.5/seafile/lib/python2.7/site-packages/s                                                                             easerv/api.py", line 713, in get_user_quota
    return seafserv_threaded_rpc.get_user_quota(username)
File "/home/seafile/seafile-server-7.0.5/seafile/lib/python2.7/site-packages/p                                                                             ysearpc/client.py", line 125, in newfunc
    ret_str = self.call_remote_func_sync(fcall_str)
File "/home/seafile/seafile-server-7.0.5/seafile/lib/python2.7/site-packages/c                                                                             cnet/rpc.py", line 75, in call_remote_func_sync
    req_id = self._start_service(client)
File "/home/seafile/seafile-server-7.0.5/seafile/lib/python2.7/site-packages/c                                                                             cnet/rpc.py", line 36, in _start_service
    raise SearpcError("Error received: %s %s (In _start_service)" % (rsp.code, r                                                                             sp.code_msg))
SearpcError: Error received: 511 Unknown service (In _start_service)

I tried both using mysql and sqlite3 db.
I think there might be a dependency (maybe version) error. Is there a list where I can find all dependencies for the Raspberry Pi 4 or do you have an idea what could be the issue?