Can you please check if the allow update checkbox for your Cost type "Resource" is checked.
The navigation is
Cost Management >> Setups >> Cost types.
Query your cost type here and see.
Also could you please tell me where exactly are you trying to update cost manually? The cost is of what material cost, overhead?
I am sorry for the delay in response.
I am trying to give manual cost for the Item in Cost window(Standard costing)
For cost element : Resource, I am not getting any thing in LOV for Cost Sub Element, That is my question.
I got the solution for this, we need to define Resource with Type as Currency, then we get values in sub element