Sometimes network drives do not map correctly, this can often be resolved by forcing windows to resync the settings from the network. To do this follow the steps below:
1. Open up the start menu and type in "gpupdate", there is no box to type in to start with but it will appear when you start typing.
2. After typing in gpupdate, open up the application to run the command by clicking on "Open"
Wait for this command to run. This will automatically close after completion and the u-drive will be restored in File Explorer.