Hi,
Regardless of virtual machine or physical devices, in order to remote from one device to another, they are either required to be in the same network segment for direct access nor connecting via VPN/RD gateway(specific role installe for remoting externally).
So kindly ensure that your Guest VM and the Andriod device could be communicated with port 3389. You can test by telnet command as below:
Using Telnet to Test Port 3389 Functionality
https://support.microsoft.com/en-in/help/187628/using-telnet-to-test-port-3389-functionality
Moreover, if you need more assistance on Hyper-V network like Hyper-V Virtual Switch, it is suggested to raise separate thread and wait for experts there.
https://learn.microsoft.com/en-us/answers/topics/windows-10-virtualization.html?sort=newest&filter=all
https://learn.microsoft.com/en-us/windows-server/virtualization/hyper-v/get-started/create-a-virtual-switch-for-hyper-v-virtual-machines
Hope this helps and please help to accept as Answer if the response is useful.
Thanks,
Jenny