racklogs give me error in redmine settings

hello guys,

i installed the plugin of racklogs and it works good no problem. but when i try to access (settings) in redmine it gives me this error:
(Internal error
An error occurred on the page you were trying to access.
If you continue to experience problems please contact your Redmine administrator for assistance.

If you are the Redmine administrator, check your log files for details about the error.)