Please help us to fix it... It displays an error as follows. "[XNRR7V010].DBO.[OSSYS_USER_T13] with key 0 was not found" 

Hi,

I guess that you are using the GetUser action of User Entitie and you are passing 0 as ID.
If you pass an Id that doesn't exist in that kind of action it will give an error.

<Edited>
Just to complement the above info check this information.

ok. Thank you. It helps.