"This accessory may not be supported" is jamming my iPhone 7 Plus

"This accessory may not be supported" has gotten on my iPhone 7 Plus, and it's not going away. I try to tap on the "Dismiss" tab, and it doesn't go away. Also, nothing on my iPhone is responding to my touches, and I can't shut the phone down. I know the correct process to do that, by holding down the right button until the slide appears on the screen. When it appears now, it doesn't respond to me trying to slide it.

Due to this, I'm currently just trying to run the battery down, so it will shut down that way.