What actually works when your Apple‑silicon Mac refuses to boot
Apple’s official guide, How to revive or restore Mac firmware, explains how to recover an Apple‑silicon Mac that’s stuck on the support.apple.com/mac/restore screen. Surprisingly, a few critical details are missing and just plain wrong. Even the screenshots are don't look like the current version of macOS.
This post documents what actually worked on my 14‑inch 2023 MacBook Pro (M2 Pro chip) after a real firmware failure and annoyingly, a Genius Bar visit on 17 Feb, 2026. Treat it as an unofficial but practical supplement to Apple’s instructions.
I do want to complement the excellent service I got at the genius bar. The tech was patient, competent and completely aware of the problem having just repaired another system in exactly the same way earlier that day.
tl;dr: keep holding power long after the others are released on the bad computer until the bad computer screen turns off.
1. Use the correct DFU key sequence — and keep holding power long after the others are released
For Apple‑silicon laptops, the DFU entry sequence is:
- With the bad Mac fully powered off, press and release the power button.
- Immediately press and hold: right Shift + left Option + left Control + power
- Hold all four keys for about 10 seconds.
- Release all keys except power.
- Keep holding the power button.
- Not for 5 seconds.
- Not for 20 seconds.
- For as long as it takes — sometimes up to 10 minutes — until the screen goes completely black. This indicates that the DFU is activated.
This is the important part. When firmware is corrupted, the Mac may cycle through reboots for several minutes before the display finally shuts off and DFU becomes available. If you let go early, DFU never starts.
If the screen is not fully black — no glow, no backlight — you are not in DFU.
2. Only after the screen on the bad mac is truly black should you connect the USB‑C cable
This is the opposite of Apple’s instructions, but it works on M2‑generation machines:
- Wait for the screen on the bad mac to be fully black then release the power button.
- Only then plug in the USB‑C cable between the two Macs.
- Be sure to follow the steps to plug in to the correct port on the bad mac. In my case it was the left most USB port while facing the left side of the computer. More at support.apple.com/mac/restore
Connecting the cable too early often causes the helper Mac to misidentify the device and drop into the wrong mode. Wait patiently while the helper mac figures out that it has a DFU mode mac attached to the USB port.
FYI. Apple says this requires a A USB‑C cable that supports data and charging. In reality, any USB‑C to USB‑C cable is fine—no need for an Apple‑branded. I didn't test this but apparently a Thunderbolt cable will also work fine.
3. If the helper Mac shows “Mac Recovery,” you are not in DFU — and revive/restore will fail
This distinction is absolutely critical:
- DFU mode → The helper Mac shows a DFU device in Finder or Apple Configurator.
- Not DFU → The helper Mac shows Mac Recovery, a drive icon, or anything resembling standard recoveryOS.
If you see “Mac Recovery,” stop. Revive and Restore will not work from this state. They will fail with vague errors like:
“Error 21."
"The Mac ‘Mac’ could not be updated.”
Only the true DFU window — black screen on the bad Mac, DFU device on the helper Mac — allows a successful revive or restore. The good computer will show the huge icon below:
Revive vs Restore: What Actually Works
Once in DFU mode, you can click on the image above to select Revive or Restore. The restore process will begin immediately and a progress bar will appear (I think it shows on both machines) and the process takes about 10 minutes.
Apple describes the two DFU actions this way:
Revive Mac
- Repairs firmware and recoveryOS
- Does not erase internal storage
- Intended as the “safe” first step
- This rarely works
Restore Mac
- Erases the internal SSD
- Reinstalls firmware and macOS
- Returns the Mac to factory settings
In real‑world firmware failures — especially those triggered by macOS updates — Revive rarely works.
If you have a Time Machine backup, Restore is usually the reliable path, although there can be some challenges. Most disappointingly, docker containers don't come back. See the image below for the time machine restore process. It takes a long time and reports that it is "starting up" for well over 1 hour especially if you have lots of files to restore.
A practical strategy:
- Say a prayer to the computer gods and sacrifice a barnyard animal.
- Try Revive Mac once from a confirmed DFU state.
- If it fails or the Mac remains unusable, re‑enter DFU and choose Restore Mac.
- Restore your data from Time Machine.
This problem came about when I tried to update my macOs to Tahoe and after about 2-3 hours, I powered off the mac as I hadn't seen any progress bar movement. Apparently you should NEVER do this. I should have waited overnight to see if it finished. In all fairness, I did update a different mac and it went quite quickly as I recall.