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Before we get into the software fixes, let’s start with the simplest solution of all: restarting your Mac. Switch the Mac off and back on again. You’ll be surprised at how many problems a quick restart solves.

• Insert the disc or USB drive into the computer that can’t boot properly and boot from the device. On Windows 8 or 10, click the “Repair your computer” option instead of “Install now” in the installer screen. Then select Troubleshoot Startup Repair to run startup repair.
• The options available in Startup Security Utility vary depending on your Mac model. See the Apple Support articles About Startup Security Utility and About the Apple T2 Security Chip. Startup Disk: Set the startup disk for your Mac. Choose Apple menu Startup Disk. To return to the Recovery app, choose Startup Disk Quit Startup Disk.

Next, check the USB device. There’s a chance that it could have failed, particularly so if you’re using a cheaper cable. Inspect the device visually, looking for damage to the connector and any signs of frayed wiring. If there is no apparent damage, take two different USB devices and test them against different ports. If the devices aren’t working on one or all of the ports it’s more likely to be an issue with your Mac and not the device.

Listen for the chime sound and let the Mac boot up as usual. Uninstall potentially conflicting apps. If the USB ports not working on your MacBook Pro or iMac is a recent issue and there doesn’t seem to be any problem with USB devices, it could be that an app is conflicting with USB functionality.

A USB device that works on one port but not another is a sign of a faulty port. If this is the case, the only real solution is to contact an authorized Mac specialist for a hardware diagnostics test and have the port repaired.

If the device doesn’t work in any of your ports, then continue reading for some potential fixes.

What to do if Mac USB devices are not working

All of your Mac or MacBook USBs not working is actually better news than one failing. It’s unlikely that all of your ports would fail at once which means the fix is probably an easy one.

Here are three things to try, starting with the most common fix.

1. Reset the SMC

Resetting the SMC (System Management Controller) is a simple fix that cures a wide range of hardware issues. How this is done depends on whether you’re using a MacBook or Mac desktop.

Resetting the SMC on a MacBook

1. Shutdown your MacBook.
2. Connect the power adapter.
3. Hold Shift+Control+Option and the Power button at the same time.
4. Release all the keys at the same time.
5. Let your MacBook boot up as usual and the SMC will be reset.

Resetting the SMC on an iMac, Mac mini, or Mac Pro

1. Shut down your Mac.
2. Disconnect the power cord.
3. Press and hold the Power button for 5 seconds and release.
4. Reconnect the power cord and switch the Mac back on.

2. Check for updates

Outdated firmware and software results in various hardware issues, including... Yep — Mac USB ports not working.

Check for system updates by opening the App Store and clicking on the Updates tab. If updates are available, click on the Update button next to each application that you want to install.

3. Reset PRAM/NVRAM

Startup Mac From Usb Stick

The PRAM (Parameter RAM) and NVRAM (Non-Volatile RAM) hold information about various USB components. Resetting them could be the solution to your USB woes.

It’s a slightly different process to resetting the SMC, but no less difficult.

1. Shutdown your Mac.
2. Restart it, holding down Command+Option (ALT)+P+R as you do.
3. Hold down the keys until you hear a sound and see the screen flash.
4. Listen for the chime sound and let the Mac boot up as usual.

4. Uninstall potentially conflicting apps

If the USB ports not working on your MacBook Pro or iMac is a recent issue and there doesn’t seem to be any problem with USB devices, it could be that an app is conflicting with USB functionality. If you’ve downloaded an app from an unknown source there is the potential for it to contain malware, which could also be the cause of the problem.

In any case, it’s worth uninstalling recently downloaded and installed apps. If they aren't the reason for the USB ports acting up, you can easily reinstall them from the App Store.

One way to remove apps is to use Launchpad or Finder. Or you can use a quicker, more effective method: CleanMyMac X.

To completely remove an app and every file associated with that app, use CleanMyMac.

CleanMyMac’s Uninstaller tool scans your entire system for every trace of an app and completely removes it. Using the tool is every bit as easy as deleting an app manually.

1. Download and launch CleanMyMac (free download).
2. Click on Uninstaller from the sidebar menu.
3. Select the app that you want to remove from the list.
4. Click Complete Removal in the Smart Selector panel.
5. Hit Uninstall.

While CleanMyMac lets you uninstall apps in bulk, in this case, you should delete apps one at a time until you find the culprit. CleanMyMac also lets you clean up unwanted junk, declutter your Mac and improve performance.

One way to uninstall apps manually is by using the Launchpad:

1. Open the Launchpad.
2. Find the app that you want to remove and click and hold the icon until it starts to jiggle.
3. Click on the X that appears in the corner of the app, then click Delete.

You can also uninstall apps from the Finder:

1. Open the Finder and go to Applications.
2. Find the app that you want to remove and drag its icon to the Trash (you might need to enter your admin credentials to confirm you want to delete the app).
3. Click on the Trash icon and select Empty Trash.

Startup Mac From Usb

Having one or more USB ports not working on your Mac can be hugely frustrating, especially if you rely on those ports for data backup and external peripherals. That said, USB problems are quite rare and are usually easy to fix. Work your way through these troubleshooting tips until you find the one that works and restore your Mac to its full glory.