Successfully download app 100% but wont install after that
I have the same problem. It get stuck at 100% and doesn't give any notifications.
Nexus 6p running Android 7.0 (not rooted).

After the app reaches 100% I close the play store (swipe it away from recent apps) and start it again, it'll install and download the next app and get stuck at 100% of the next app.

I am repeating the process to download the updates but it is by no means a fix to the problem. But atleast your apps will be updated.