How to Troubleshoot Mac USB Issues (7 Steps)

Check that the USB device is connected to the appropriate jack. There is a USB jack in the back of most keyboards, but it often only works with a mouse.
Unplug any USB devices and wait a few moments before reconnecting them. You can often fix problems with your USB keyboard and mouse by using this method. Try restarting your computer if the malfunction persists after you reconnect the USB device.
Test your USB peripherals in another computer. If the problem exists in the second computer, you may need to have the device serviced or look for an updated version of the firmware that supports your USB item. Check the manufacturer's website for these updates.
Try different devices in the same USB port. For example, if your mouse if behaving strangely, see whether an external drive or an iPod is able to connect to the computer via that USB port.
Disconnect any USB hubs that you're using and connect each device one at a time to your computer. You need to troubleshoot the devices individually to find out whether the USB hub or the one of the devices is causing the problem. Be sure to test each peripheral with a working USB cable.
Reset the parameter random access memory (PRAM) and nonvolatile RAM (NVRAM) on your computer. Turn off your computer, then restart it and immediately press and hold the 'Command,' 'Option,' 'P' and 'R' keys on the keyboard. Release the keys after you hear the startup chime for the third time and your computer should boot normally.
Consider reinstalling the operating system after clearing your computer's hard drive. Be sure to back up all of your data before you erase the disc. You may also want to bring the computer to a Mac service center and have the logic board examined.
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