MPLAB ICE 4 In-Circuit Emulator User's Guide

8.2.5 USB Port Communication Error Actions

The problem is most likely caused by a faulty or non-existent communications port:

Reconnect to the MPLAB ICE 4 In-Circuit Emulator.
Make sure the debugger is physically connected to the computer on the appropriate USB port.
Make sure the appropriate USB port has been selected in the debugger options (see section Debugger Options Selection).
Make sure the USB port is not in use by another device.
If using a USB hub, make sure it is powered.
Make sure the USB drivers are loaded.

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