Can not reload my Plugin - help

i login in the admin console(htpp://xxx.xxx.xxx.xxx:9090) ,

open the page which is “http://192.168.0.99:9090/plugin-admin.jsp”, and click the restart button on my Plugin.

but it un-successful.

i saw the eclipse print logs is : “Error unloading plugin xxPlugin. Will attempt again momentarily.”

i thought , it may be the plugin dir can not delete.

and how i do? ?

thank you.