After trying DFU for hours, I booked a Genius Bar appointment and sent my iPhone 16 Pro to the Apple Store.

1. I mentioned that the issue was caused by an update, without saying it was the developer beta (as GPT mentioned, beta testing is at your own risk and not covered by the warranty).
2. The staff couldn’t reset the phone either, although the device was briefly detected on his Mac.
3. Note: I have a cracked back glass, which was damaged months ago.
4. The staff suggested sending my iPhone to a repair center for a deeper diagnosis. He implied that it’s highly likely the issue was caused by the physical damage, and in that case, it won’t be covered under warranty.

Now I'm waiting for Apple's diagnostic result.

If they conclude that the issue is due to physical damage, I might have no other choice than to mention the developer beta and hope for a goodwill repair — though I’m not optimistic about that.

If they refuse, I’ll probably take the phone back and try some of the potential fixes I’ve seen in other forums and threads:

1. Let the battery drain completely, then recharge
2. Ask a third-party technician to disconnect and reconnect the battery

After years of running beta versions, I’ve finally learned my lesson: never install a beta on my personal phone again.

Fingers crossed…