Issues with IOS 15.4.1 on iPhone 12

My iPhone 12 recently automatically downloaded and installed the newest IOS. Before the update, the phone was working perfect. Now there are several issues with my phone. The notifications for messages will not work. I have tried restarting the phone, turning all notifications on and off and specifically messaging notifications. No luck. Now I find iTunes will not recognize my iPhone so I cannot revert back to the last working IOS version on my phone. Any suggestions/help would be greatly appreciated. Thanks!