black screen

Which button combination are you using - this one?

1. Quickly press and release the Volume Up button.
2. Quickly press and release the Volume Down button.
3. Press and hold the Side button until the Apple logo appears, then release the Side button.

I've had my iPhone XR for almost a year and I've ran into this issue twice. Currently, I'm waiting on my 3rd phone to be shipped to me. In short, if the method above doesn't work, which it probably won't, you'll have to get it replaced. Hopefully you still fall in the one year warranty period, otherwise you'll be hit with a 400-500 fee. In summary, its an ongoing issue that apple has yet to fix. Look to purchase insurance for future repair service through your service provider or apple. Hope this helps!