Redmine

We have installed the plugin crm in a test installation with this setup:

Environment:
  Redmine version                2.5.2.devel
  Ruby version                   2.1.5-p273 (2014-11-13) [x86_64-linux-gnu]
  Rails version                  4.1.8
  Environment                    production
  Database adapter               Mysql2
SCM:
  Mercurial                      3.1.2
  Git                            2.1.4
  Filesystem                     
Redmine plugins:
  redmine_contacts               4.0.4
  redmine_work_time              0.3.1

To begin the List of contacts is empty, thats normal. But There is no button to insert new items. I can see one field for searching contacts and nothing else in the main frame of browser window. I tought I had to give the rigths, but it makes no difference. Do you have an idea, what I havo to do?

Thanks and best regards
Udo Forstmann