I just upgraded to build 28. The first time I ran TCC (from a previously hand-made desktop shortcut) I got the UAC prompt. I said no. Then build 28 started and told me it had expired. I clicked "Register", then "Cancel" and not it's working OK. And when I started v15 from a pinned shortcut, it also gave me the UAC prompt. I said "Yes" and now I'm back to normal.