VPN connects but can't access network locations in Windows Explorer

Hi,
I'm running Windows 10 inside Parallels Desktop 12 for Mac Pro Edition. Mac is running macOS Sierra.
In Windows I'm trying to connect to my work VPN. The VPN Type is PPTP.
It connects just fine, but I can't access any network locations in Explorer e.g. "\\machinename\c$"
Trying to go to a location on the network just says "Network error. Windows can't access..."
I can access locations by using explicit IP address e.g 192.168.x.x
Pinging a machine name looks like it works, but the IP is wrong - it says 104.20.90.82 as opposed to 192.168.x.x
Any help much appreciated.