Did you uninstall cc 2015? If you still have it did you try to open that clip in it successfully? cc 2017 is so friggin’ weird I had to go back to cc 2015.4. All sorts of problems with my opacity pen tool. Yesterday I tried installing again, and now the opacity tool draws a mask but nothing happens, it doesn’t mask out anything.
If you googled the problem and nothing came back you’ll have a long wait. It means no one else has had that problem. You might want to try re-installing it, if anything.