when attach file to a lease i get message " you have encountered unexpected error please contact sys

Dears;

IN Oracle EBS property management ! when try to attach any document or file  or image to a lease contract (in Draft Mode) ! I get system error message without any error number ! just a message line such as :

(error Page) : you have encountered unexpected error please contact system administrator for assistance ".

so any assistance or support or hint to overcome this problem issue ? is it related to file size limit or network or brawser or maybe fomat of some sort !

Thank you.