I phone 11 is dark and won't turn on, any ideas of what causes this

Hey there,

Try to force restart your iPhone:

Press and quickly release the volume up button, press and quickly release the volume down button, then press and hold the side button. When the Apple logo appears, release the button.

Also try to charge it if it won’t charge learn what to do ☞ If your iPhone or iPod touch won't charge - Apple Support

Also We recommended you to check this article if the instructions above doesn’t help ☞ If your iPhone won't turn on or is frozen - Apple Support

It might be a bug within iOS. iOS has become very unstable, and in recent updates they have been trying to make iOS stable again. Still far more stable than android, but at WWDC they should be fixing all of these issues. If it’s not a bug, it might be an issue with the phone itself, which is probably the case since bugs are fixed usually with a quick restart. Is the phone on, but with a black screen? Have you tried force restarting the phone. To force restart the phone, press and quickly release the volume buttons (both). Then, hold down on the power button until apple logo appears. If this solution does not work, then it might be an issue with the phone itself. Could be water damage or another mechanical issue.

Well, when was the last time that you replaced the battery for the iPhone 11?