cant edit excel file/ cant open a new file

[kimdada]

please help, I was trying to attach the error I encountered while accessing my excel file but I cannot find the icon for the attach file. I cannot edit my excel file and cant even open a new one it says product activation failed. what does it mean.
thanks

 

[mole999]

You can't add files here. Product activation refers to MSOffice, it needs reattaching to a activated licence via Microsoft, either a trial has expired or something else