What should I do if my iPhone is not available?
The spare phone at home was used by my child, who doesn't go to school on weekends and plays a lot on the phone. After changing the password, they probably tried to unlock the device, and now the iPhone is in the "Unavailable" state. I know the unlock password and Apple ID password, but how can I fix this "Unavailable" state?
The status “Not available” means that someone (in this case your child) has tried the unlocking several times without success. This has nothing to do with your Apple ID.
If you really know the unlock password, you can unlock the iPhone; You don’t get the “not available” status as long as the device can’t register for new unlocking attempts in the Apple system.
You can check if the iPhone is online when you try to get it through the browser http://www.icloud.com and Find My iPhone. If it is online, you can unlock it via the browser.
Otherwise you have to wait until the device is available for new unlocking attempts. It can take several hours.