You must have done a lot of ghost feeding to get to 40 ppm nitrate, lol. Or you’ve got nitrITE in the water that’s screwing with the nitrATE test. Did you add a bacteria source, or live rock or was it dry rock and ghost feeding only? Pic would be good.
Here is a picture of the tank.
I used dry rock and dry sand and biospira for the bacteria.
I used pellets to ghost feed the tank. Maybe I overdid myself like you said