Can not Map a network drive

We are running a server with several users. One of those user has mapped his F drive to the server. Rest all users are able to access the server comfortably without any problem, they can even ping the server but that particular user is facing some problems. Whenever he tries to access the mapped drive, a pop up message appears saying “The device is not ready.”

When we try to delete the same, another pop up appears saying “The Network connection could not be found." This drive is containing 100s of important project files and we are not able to access the same. Please help.

It seems like i managed to fix the problem my self. I guess the problem was because that user was using a Pendrive and she use to eject the drive by pulling out directly without using "safely removing the device" option. Now as evey time he use to do the same, not removing properly, it would assign a new drive letter and it didn't care if that drive was already taken. Hence the other drives were talking over the letter F. We fixed the same and problem gone. Thanks by the way.