Long text area filed in not visible in filter section of the report?

In an custom object I have created a long text area field. In sandbox we can add the filter for the long text area field but in production if I search the field in add filter section the result will show as not found. I found that previously in the  field encrypted check box was checked but I have removed the check box now sill it is not working. I have tried to logout and login as well still same result. Is there any way to solve this?