Hi Priyanka,
If you are using a prompt page, you need to make sure to have the following option:

(Note: Required is... not required, but Multi-select is required)
and [Sales (query)].[Products].[Product line]
in ?Product line? in the filter (in for multi-select or = for a single value).
If you are using a package, you can use the
Build prompt page option:

Best regards,
------------------------------
Patrick Neveu
Positive Thinking Company
------------------------------