Blank screen after update

Just experienced the same. iPhone 7 Plus. Updated on Saturday to latest software. Today suddenly the screen went black and the lock button wouldn't turn it on or do anything. Plugged it into iTunes and the screen eventually came back - but nothing was working except the home button. Tried to restore it . Couldn't as "find my iPhone" was on - can't turn it off as the touch screen is unresponsive! After about 3 minutes it suddenly came back to life - but this is a new phone with the latest software update. This bug stopped the screen AND lock button working - I totally rely on my phone, I'm a Carer, mum to four and it's a lifeline.

How to force restart

You should force restart your iPhone, iPad, or iPod touch as a last resort, and only if it's not responding. Follow these steps to force restart your device:

• On an iPhone 7 or iPhone 7 Plus: Press and hold both the Sleep/Wake and Volume Down buttons for at least ten seconds, until you see the Apple logo.
• On an iPhone 6s and earlier, iPad, or iPod touch: Press and hold both the Sleep/Wake and Home buttons for at least ten seconds, until you see the Apple logo.

If your iPhone, iPad, or iPod touch won‘t turn on
Please let me know if you have any questions.
All the best.

You can't force restart with this bug as it disables the lock button too... you haven't read the post properly.

What did you then. I’m going thru the same thing.

General > Reset > Reser all settings. That worked for me