Brad Smith, from Facebook
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Last Thursday, MacBook decided to not charge and not recognize power source.
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Symptom: New Mac M4 Pro chip, was bouncing off my USB connection to my mixer, keyboards and pedals.
TLDR: “Allow accessories to connect” (see below)
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How the story goes
I got a new MacBook Pro 14” with M4 Pro chip and 24GB RAM.
This one has fancy control of power, charging and now it also dabbles in allowing USB connections (or NOT).
Posting this in case you run into it. The new Mac was intermittently losing its connection to my USB hub, mixer, pedals and keyboards. Causing Gig Performer to show the scary RED SCREEN of lost connection.
Thankfully, you can turn off the “smart” function and ALLOW ALL CONNECTIONS.
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About Mac charging
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Why USB-C Icons May Differ from MagSafe
- “Plug” vs. “Lightning” Icons:
- On macOS, a lightning bolt icon means the battery is actively charging.
- A plug icon means the Mac is running off the power adapter, but the battery is not charging.
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Charging on Hold: This “plug” state often occurs if Optimized Battery Charging is active, holding the charge at 80% to preserve health. It can also happen if the power source provides enough energy to run the Mac but not enough to simultaneously charge the battery (common with lower-wattage third-party USB-C bricks).
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Third-Party Identification: Some third-party USB-C chargers (like Anker GaN chargers) trigger a “plug” icon initially as part of Apple’s identification strategy before reverting to a normal charging symbol.
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Reasons for Intermittent Behavior on USB Ports
If your Mac intermittently drops the power icon entirely or behaves differently across the three ports, consider these factors:
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Cable and Wattage Limits: Not all USB-C cables are created equal. Some are limited to 60W or 100W. If you use a cable that can’t provide the Mac’s required wattage (up to 140W for the 16-inch M4 Pro), the connection may be unstable or insufficient to trigger the “charging” state.
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Port-Specific Hardware Issues: While rare on a 2024/2025 model, individual ports can experience hardware failures or debris buildup. If one port consistently fails to recognize power while others work, the port itself may be faulty.
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Thermal Throttling: If you are charging on one side of the Mac while using high-bandwidth accessories on the same side, the ports may temporarily reduce power intake due to heat proximity sensors.
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Negotiation Speed: USB-C (Thunderbolt) requires a complex “handshake” between the adapter, the cable, and the Mac to determine power levels. MagSafe uses a more direct proprietary protocol that often registers “connected” status faster and more reliably in the UI.
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Troubleshooting Steps
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[1] Check Battery Health Settings
Go to System Settings → Battery and click the (i) next to Battery Health. If “Optimized Battery Charging” is on, the Mac will frequently show the “plug” icon instead of charging.
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[2] Clean the Ports
Use compressed air to ensure no debris is blocking the pins in the USB-C ports.
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[3] Test with the Original Apple Cable
Use the Apple 140W USB-C Power Adapter and the official cable to see if behavior stabilizes across all ports.
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[4] Run Apple Diagnostics
Restart your Mac and hold the Power Button until “Loading startup options” appears, then press Command + D to check for hardware faults in specific ports.
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[5] macOS Settings - Allow Accessories to Connect
In macOS settings, you can adjust security preferences for USB devices.
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Go to Apple menu > System Settings.
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Click Privacy & Security in the sidebar.
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Scroll down and select the pop-up menu next to “Allow accessories to connect” and choose “Automatically When Unlocked” or “Always”.