Just installed PRTG on a Win Server 2016 Hyper-V VM, and right from the start the Probe Health sensor gave me the error "Probe disconnected".
Please verify that the PRTG probe service is running on the server PRTG is installed and the probe is able to connect via Localhost (only Local Probe). You can do this through the PRTG administration tool.
Disclaimer:
The information in the Paessler Knowledge Base comes without warranty of any kind. Use at your own risk. Before applying any instructions please exercise proper system administrator housekeeping. You must make sure that a proper backup of all your data is available.