The below information was taken from here: "Peer Name Resolution Protocol" will not start?
From an elevated CMD prompt.
Net stop p2pimsvc /y
Then delete the following file. "C:\Windows\ServiceProfiles\LocalService\AppData\Roaming\PeerNetworking\idstore.sst"
reboot and you should be able to rejoin the homegroup.
Let me know if it works or not.