How to set automatic build after a merger request by GitLab

[Fatiha]

Hello ,

   I try to configure jenkins to automate builds after every merge request on GitLal , by using gitlab-merge-request-builder-plugin , i set the configuration like mentionned in documentation's plugin. But it does not work as i want. the build is not automatic !! And when i lunch it manually, it gives me this :

Any help please :)
thank you in advance
  

[Fatiha]

I want to add these screencats wich show you how i configure the plugin:

Thank you in advance :)