When performing an update, your Mac gets stuck on the "Setting Up Your Mac..." window as seen below:

Setting Up Your Mac
"Setting Up Your Mac..."

The "Setting Up Your Mac..." message means that the update is finished but it is unresponsive because of the possibility that it is not booting up successfully.

Force Reboot your Mac

To reboot your Mac, press and hold the power button on your Mac for a few seconds until it turns off. Wait for a few more seconds, then switch your Mac back on again. It should now start up normally.

To learn more about Mac force reboot, refer to this Apple Knowledge Base article:

Reset the System Management Controller feature on your Mac

This useful tip can fix a wide variety of system problems on a Mac. Resetting the System Management Controller or SMC can fix issues with Mac slow performance, startup issues, and Wi-Fi hardware concerns. Doing this will not remove any data stored on your Mac.

To learn more about resetting SMC, refer to this Apple Knowledge Base article: