This can happen for several reasons, mostly related to too much bogus traffic hitting your RDP port. It is best practice to only allow RDP access to a limited set of static IP's, only access via firewall or if the other two options are not possible change the default port for RDP access to help limit default bogus traffic.
With that said, the quickest way to solve this problem without a reboot is to simple disable the network adapter and reenable it.
Step by Step:
- Login to your Hyper-V manager
- Connect to the Guest VM in question
- Open the network manager and change adapter settings or Control Panel\Network and Internet\Network Connections
- Once on this screen simply right click the adapter and disable, then reenable.
Thats it, your issue should now be solved.