You ran the macOS Sierra update, the MacBook restarted — and now nothing. The screen stays black, there’s no startup chime, and the machine seems completely dead. Before you assume the worst: Sierra was a 2016 release that ran on Intel Macs, and a failed post-update boot usually comes down to corrupted power-management or firmware settings you can reset yourself. Work through these steps in order.
Step 1: Rule out a power problem
Start with the basics. Plug in the original Apple power adapter — a third-party charger may not deliver enough power — and check the MagSafe indicator light. Try a different wall outlet, then leave the MacBook plugged in for 10–15 minutes before pressing the power button once. A fully drained battery can mimic a dead machine. If your other Apple gear also misbehaves around charging, see our guide on why an iPhone stops charging from a computer after an hour.
Step 2: Reset the SMC
The System Management Controller handles power, the battery, fans, and the power button — and an interrupted update can leave it in a bad state. Apple documents the SMC reset in its Mac support resources, and 9to5Mac has covered it in detail. For Sierra-era Intel MacBooks with a non-removable battery:
- Make sure the Mac is shut down and connected to power.
- Hold Shift + Control + Option on the left side of the keyboard, then press Power at the same time.
- Keep all four held for 10 seconds, then release.
- Press the power button once to start the Mac.
On Apple Silicon Macs this isn’t needed — just hold the power button for about 10 seconds to force a restart.
Step 3: Reset NVRAM (PRAM)
NVRAM stores low-level settings like the startup disk and display resolution. On Intel Macs:
- Press the power button to turn the Mac on.
- Immediately hold Option + Command + P + R before the gray screen appears.
- Keep holding for about 20 seconds — on Sierra-era machines you may hear the startup chime twice.
- Release the keys and let the Mac boot normally.
Step 4: Boot Recovery and repair the disk
If the Mac still won’t boot, hold Command + R right after pressing power to enter Recovery Mode (on Apple Silicon, hold the power button until the startup options appear). Then:
- Choose Disk Utility from the Recovery menu and click Continue.
- Select your startup disk in the sidebar and click First Aid.
- Let it repair any file-system errors the installer left behind, then restart.
Step 5: Reinstall macOS from Recovery
Still nothing? From the Recovery menu, choose Reinstall macOS. This replaces the system files while preserving your user data in most cases. Let the installer finish without interrupting it, even if it looks stuck for a while.
If it still doesn’t work
Contact Apple Support or visit an Apple Store. An update can expose a hardware fault that was already lurking — a failing SSD or logic board — and Sierra-era MacBooks are now past their warranty window, so weigh repair cost against replacement. Once you’re back up and running, see our guide to setting up automatic hotspot connection from iPhone on Mac.
Frequently asked questions
Will reinstalling macOS delete my files?
In most cases, no. Reinstalling from Recovery replaces the operating system files but leaves your documents, apps, and settings in place. Still, keep a backup if you have one — if the drive itself is failing, a reinstall could make recovery harder.
Do these steps work on modern Macs too?
Only partly. The SMC and NVRAM resets here are for Intel Macs, which is what Sierra ran on. Apple Silicon Macs don’t have an SMC to reset and enter Recovery differently. For a newer machine, check our modern Mac guides — like how to quickly open the installed apps list in macOS 26.
Conclusion
A MacBook that refuses to turn on after the Sierra update feels catastrophic, but the fix ladder is simple: check power, reset the SMC, reset NVRAM, repair the disk in Recovery, and reinstall macOS as a last resort. One of these steps revives the vast majority of machines.
