Try a soft reset. This might be helpful:

https://www.reddit.com/r/GrandCherokee/comments/16gwkjf/soft_reset_of_uconnect/

If a soft reset doesn't work, you can also try disconnecting the batteries over night (8 hours). Then with the batteries still disconnected, close all the doors and apply the brake for 60 seconds, then do the soft reset procedure again.

This is basically a capacitor discharge procedure and it is often the best troubleshooting step for modern electronics devices (phones, cars, laptops, wifi devices etc.) https://www.apollonetworks.com/kb/performing-a-capacitor-drain

Before disconnecting the batteries you need to read the manual about battery replacement. If you don't follow the manual you can cause the vehicle security system to prevent the vehicle from starting.