Occasionally the network drive gets grumpy and dimounts from the M drive, and neither the Easy Search utility nor mapping tool in Windows Explorer will re-map it.
In this case, the best solution is to re-start the disk drive:
Click and hold the Power button on the front of the drive until it blinks,
and then wait for the drive to shut down.
If the light does not blink, then pull the plug.
Click the Power button again and wait for the drive to re-start, and both drive lights turn blue.
If either of the drive lights is amber, then that drive has failed and must be replaced.
Use the Easy Search utility, or Windows Explorer to re-map the network drive to the local drive letter M on the computer.