It is common when trying to save  documents from many applications, that network drives are not listed as an option to save to even when they're mapped. To make them a visible save location:

1. Open the registry on the PC to:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System

2. Create DWORD EnableLinkedConnections set the value to 1

3. Reboot

4. Try replicating the issue, should be corrected.