If UAC is enabled and Admin Approval Mode is enabled for the built-in Administrator for example, you might have problems accessing network drives from an elevated command prompt. This behavior is expected, since in Admin Approval Mode all apps run as a standard user by default. If a program is elevated, it runs under a different session than the non-elevated user.

Microsoft suggests following fixes or workarounds:

  1. Remap network drives via bat file or manually
  2. Create this registry key, which creates a link between both sessions:
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System DWORD EnableLinkedConnections 1