Follow the steps below if nothing is showing in the chat window or JCEF.
1. Select Help > Find Action from the menu.
2. Look for Registry...
3. Find the ide.browser.jcef.sandbox.enable option in the list and disable it
4. Restart
ref - https://github.com/flutter/flutter-intellij/issues/7000#issuecomment-1952854934
If the error is still the same, try invalidating the embedded browser caches.