Offset path just duplicates path without offsetting

[holly23419974]

Why when I try to offset my path does it just duplicate the same path each time?

happens when I go object - path - offset  & effect - path - offset 

when I click preview it does show any offset and then when I click 'ok' it has just duplicated the path. if I then expand this it's just a an duplicate  

Please help! thak you!

[Doug A Roberts]

What are your offset settings?