Hi,
First, make sure are running the latest version of Negative Lab Pro (v2.1.2 as of posting). It improves the way that LR white balance is handled for the negative through the use of new dcp profiles with a dual-illuminant target.
If you run into this error, you can just change the white balance from “As Shot” to “Auto”.
Or, if you may find that the wb picker will work if you first change the profile from “embedded” to “Negative Lab” - this will make the photo appear darker (a truer representation) and should allow you to pick off the border in most situations. But again, nothing at all wrong with choosing “Auto” in this situation.
Cheers!
-Nate
Creator of Negative Lab Pro