This week I upgraded and messed with my GP 2015 installation as part of a support case. At some point, I started to get the "New code must be added" dialog box every time I launched GP.
I clicked on Yes and then logged into GP, but it appeared the next time I launched GP. I tried Run as Administrator, clicked Yes, and logged in. But it still kept appearing.
I finally stopped and thought for a second. I searched my GP 2015 directory for *.cnk files. And there I found tautil.cnk. I don't know how it got there or why it was there. I already had the TAUTIL.DIC dictionary in the directory, and had it listed in the Dynamics.set file.
My only guess is that perhaps the dictionary was updated as part of the hotfix I installed, and for some reason it failed to unchunk.
I deleted the tautil.cnk file and the New code message went away.
Problem solved, mystery remains.
UPDATE: A reader makes a good point, which I also pondered later, that the better approach is to probably rename the existing dictionary and let GP unchunk the cnk file, in case the dictionary was not successfully updated. In my case, since it was only PSTL / TAUTIL, and it was on my development machine, it wasn't a concern, but in a real environment, renaming the existing dictionary is probably the more prudent approach.