Your MacBook was working perfectly with your external monitor, but now after waking from sleep, the display stays black or shows “No Signal.” This frustrating issue affects productivity and can feel urgent when you need your dual-screen setup working immediately.
Step-by-Step Fixes
Step 1: Quick Cable Reset
Unplug your monitor cable from both ends, wait 10 seconds, then reconnect firmly. Start with the monitor end first, then plug into your MacBook. This simple action resolves connection issues in about 30% of cases. While reconnecting, check for bent pins or debris in the ports.
Step 2: Force Detection Through System Settings
Open System Settings > Displays while your monitor is connected. Hold the Option key and click “Detect Displays” button that appears in the bottom right. This forces macOS to scan for connected displays. Best used when your MacBook seems unaware a monitor exists.
Step 3: Reset the SMC (System Management Controller)
Shut down your MacBook completely. For MacBooks with Apple Silicon (M1/M2/M3), wait 30 seconds then power on. For Intel MacBooks, press Shift-Control-Option on the left side plus the power button for 10 seconds. Release all keys, wait a few seconds, then power on. This reset fixes power delivery and port recognition issues.
Step 4: Safe Mode Boot Test
Restart your MacBook and immediately hold the Shift key (Intel) or hold the power button until you see startup options (Apple Silicon). Select your startup disk while holding Shift. Safe Mode loads only essential drivers, ideal for identifying software conflicts. If your monitor works in Safe Mode, third-party software is likely interfering.
Step 5: Create a New User Account Test
Open System Settings > Users & Groups. Click the lock, authenticate, then click the plus button to add a new administrator account. Log into this fresh account and test your monitor connection. This step isolates user-specific settings corruption, not recommended when you’re in a time crunch but effective for persistent issues.
Step 6: Terminal Command Reset
Open Terminal from Applications > Utilities. Type this command exactly:
“`
sudo pmset -a hibernatemode 0
“`
Press Enter, type your password when prompted. This disables deep sleep hibernation that sometimes breaks external display detection. Restart your MacBook after running this command.
Likely Causes
Cause #1: Thunderbolt/USB-C Power Delivery Confusion
Modern MacBooks use the same ports for charging and displays, creating power negotiation conflicts after sleep. Your monitor might not receive enough power to wake properly, especially with USB-C connections.
Check for it by trying a different port on your MacBook. M1/M2/M3 MacBooks handle power differently on each port. The leftmost ports often provide more stable display connections.
Fix it by using a dedicated Thunderbolt cable instead of generic USB-C, or connect your charger to a different port than your monitor. Thunderbolt 3 or 4 cables, while pricier, prevent most power-related display issues.
Cause #2: Display Sleep Settings Mismatch
Your MacBook and monitor have separate sleep timers that can fall out of sync. When wake timing conflicts occur, the monitor might not receive the wake signal properly.
Check System Settings > Lock Screen and System Settings > Energy Saver. Note the sleep timing for both computer and display. Also check your monitor’s own menu for sleep or power save settings.
Resolve this by setting your monitor’s built-in sleep timer to “off” or “disabled,” letting macOS control all sleep behavior. Alternatively, set both devices to matching sleep intervals.
Cause #3: macOS Display Profile Corruption
Each time you connect a monitor, macOS creates a display profile storing resolution, refresh rate, and color settings. These profiles can corrupt during unexpected disconnections or system crashes.
Identify corruption by checking if other monitors work fine, or if this specific monitor works with other computers. Profile issues are monitor-specific, not port-specific.
Fix by navigating to ~/Library/Preferences and moving these files to trash:
- com.apple.windowserver.plist
- com.apple.windowserver.displays.plist
Then restart your MacBook. macOS will recreate fresh display profiles.
When to Call Expert Help
Contact Apple Support or visit an Apple Store when these symptoms appear: all ports fail with multiple monitors, the issue persists across different user accounts and Safe Mode, or you see graphics artifacts before sleep. Hardware failure signs include ports feeling loose, visible damage, or burning smells near ports.
Professional diagnosis becomes essential when your work depends on external displays. Apple technicians have specialized diagnostic tools that test port functionality beyond what users can access. Book a Genius Bar appointment through the Apple Support app for fastest service.
Consider your monitor manufacturer’s support too. Some monitors need firmware updates for proper macOS compatibility, especially with newer Apple Silicon MacBooks.
Copy-Paste Prompt for AI Help
“`
My MacBook model [insert model/year] running macOS [version] won’t detect my [monitor brand/model] after waking from sleep. I’ve tried: [list what you’ve attempted]. The connection type is [HDMI/USB-C/Thunderbolt]. This started happening [when/after what change]. The monitor works fine with other devices. What specific troubleshooting steps should I try for this exact setup?
“`
Remember that external display issues after sleep are incredibly common in 2025, affecting even the newest MacBook models. The solutions above resolve most cases within minutes. Stay calm, work through each step methodically, and your dual-screen setup will likely return to normal functioning.