This happened to me and I was able to access the voice activated app by trying different buttons. I said "go to google" and then searched for the app. Since it was installed already, I was given the option to uninstall. This fixed it.
I had the same problem. I downloaded the fingerprint app and it wouldnt let me into my phone. I clicked on ad at bottom of app when I got to internet I searched for uninstall app. It took me to a free ap that uninstalls apps. Asked me if I wanted to open it. I did and uninstalled the fingerprint app