A couple of thoughts:

1. If I recall correctly from your other post, your Medallion status just showed up on DL's computers yesterday. It's quite possible that the DL and NW computers only exchange updated elite statuses on some regular interval (e.g., every other Tuesday), so you might need to wait a bit for NW to "see" your status.

2. Did you tell NW your DL status was brand new and/or have them pull your DL # out of your PNR then re-enter it? On both DL and NW, your record reflects the status you had when you booked a ticket. If your status increases after you bought a ticket, you need to have an agent delete your FF# from your record, then re-enter it, at which point your new status will reflect (this is true even if flying NW with a NW # or DL with a DL #). If you aren't absolutely certain this has already been done, your first move should be to call NW and ask them to do the delete and re-enter your SM# and see if that causes your status to reflect.