iMessage notification and syncing between iPhone/ipad

Since updating to iOS 18.6 I am having trouble with iMessage syncing between iPad and iPhone and receiving notification. I have tried all the recommended steps: logging out, logging in, restarting, turning off “use on iPhone”, all of it. Also he notifications are not consistent, sometimes the sound plays, sometimes not. Since you can’t uninstall and reinstall the messaging app, I am hoping for solutions. iPhone 16Pro