DLC’s unavailable

If all the dlc is located on disc two, I would recommend downloading again but this time use disc two first. Hope this helps!

This is odd and usually should not be the case.

A hard reset may solve this problem.

Hold down the power button until the system shuts down and unplug the power cable.

Wait for 5 min and plug it back in and restart the console.

Sales usually end/change on Tuesdays so chances are the service alert will be fixed by then.

If not it's possible they may extend the sale

If you click on the game's icon and click manage game and add ons is the dlc in there. You should be able to download it from this menu.

If the hard reset didn't solve your problem maybe try getting the discs cleaned? Or as above try installing the 2nd one first? Hope you manage to fix mate New Vegas is a great game