IPhone unavailable

No one in this user-to-user forum can answer a question that begins with “why”. If it doesn’t let you enter a passcode you will have to restore your phone.

If your device has iOS 15.2 or later installed, you can reset it without a computer; check out this link→How to reset your iPhone, iPad, or iPod touch when you forgot your passcode - Apple Support. Otherwise you will need a computer:

See this Apple support link→If you forgot the passcode on your iPhone, or your iPhone is disabled - Apple Support

Or watch this companion video ⬇️

After restoring the phone using one of the methods above you can restore your most recent backup.

Hello nutrinancy!

Here’s what to do If you see an iPhone or iPad unavailable message or Security Lockout screen - Apple Support.

What countdown are you referring to? Please provide more details.

I hope this is helpful. Good Luck!

What do you mean by a brute force attack? It is impossible for anyone to unlock an iPhone who does not have physical possession of it.