Hi Jeff. That error is what pops up if you try to create a join link on a curve, which isn't allowed. If you try to create a link between two regular boundary points, does that work? If you constructed your parcel in its correct space but joined it without any links, then it's probably just floating there without being topologically connected to the surrounding parcels, albeit in the right place. So you'll want to rejoin it and establish the links. Also, after choosing Append File... if you just click Close, the parcel will come in as unjoined if that's ever something you'd want to do.