There is a dynamic block group available where people will answer these types of questions and the moderator will probably send you in that direction. That said, your hatch needs to be associative and a few more lines need to be added so that you have a closed area for the hatch to be associated. I modified your block per the directions below.
1. Added lines to close out the pattern area.
2. Added constraints to the lines
3. Re-hatched with associate box checked.
4. Converted lines to construction lines so they are not visible.
Hope that helps. You might want to search the dynamic block group for other ways to manipulate hatches. There are a few posts that deal with scale, angle, and origin. Really cools stuff.
