Are you seeing an Activation Lock?
If you are, you need the Apple ID and password that was used when the device was first set up. If you don’t know that, you can’t remove the Activation Lock.
If this is a used device, the previous owner needs to go to https://www.icloud.com/find/ and erase the device, then remove it from their account. If they won't do that, the device is useless. Apple won't unlock it.
Turn off Activation Lock - Apple Support. *
If you are the original owner, contact Apple. Apple can remove the ID if provided the required paperwork to include the original purchase receipt with the serial number on it.
Request additional support for unlocking your device. -
You used to be able to take the device, the original purchase receipt with the serial number, and a photo ID to the nearest Apple Store (if it has reopened) and have them remove the ID. This may have changed, so call the store before going to make sure they can help.
Genius Bar Reservation and Apple Support Options - Apple. -
If you aren't seeing an Activation Lock, some things you can try. Do you have access to another WiFi network where you can try? That has worked for several people.
Try a restart.
Restart your iPhone *
Restart your iPad. *
Try a forced restart. See the section towards the end of the article.
Reset Device. -
If necessary
Hard reset. -
Do a backup and try a factory reset. Then restore from the backup.
Restore to Factory setting. *
Restore - If you see an error when you update or restore your iPhone, iPad, or iPod. *
Backup - Restore your device from an iCloud or iTunes backup. *