Diagnosis
The touchscreen has likely frozen, which is a software glitch, not a broken screen. A simple reboot often fixes it.
How to Fix It
Let's do a soft reboot first. 1) Unplug the power cable from the back of the Alien router. 2) Wait a full 30 seconds—count it out. 3) Plug the power cable back in firmly. Let the router boot up completely (the light ring will settle into its normal color). Now try the touchscreen. If it responds, you're good.
If That Didn't Work
If the screen is still dead after a reboot, you'll need to manage the router from the AmpliFi app on your phone. The touchscreen is convenient, but all the same settings are in the app. As long as the router is working and your phone can connect to its WiFi, you can use the app for everything.
Heads Up
Avoid using cleaners or liquids on the screen. A dry, soft microfiber cloth is all you need. If the screen is physically cracked or damaged, that's a hardware issue requiring support.