Clearing out old phone.
Have a hard time clearing out my old phone. It's saying verification failed, but I have the correct PW.
iPhone 11
Not sure what "clearing out" might mean. but the following instructions will completely clear things out.
What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support
The phone will now look like it did when you first took it out of the box and powered it up for the first time.