I found this solution works for me - following the post at, https://answers.microsoft.com/en-us/windows/forum/all/grayed-out-services-in-windows-10/346bd141-13e2-42de-b93a-c4481b23ec43?page=4
after use Regedit to change the Dnscache's start type to auto=2,
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\Dnscache, and locate Start registry key
Change Startup type : =2
and restart the pc, the DNS CLIENT SERVICE status turns into STARTED, and the mapped drive works now.
Many thanks for your support, thanks to other post sharing their solution.