Cannot See And Share Files In HomeGroup
Some more to try, from the article Windows 7 HomeGroup not working? Try these quick fixes :
Visit Action Center
Click the flag icon in the Notification area of the Taskbar and click Open Action Center. Select Troubleshooting > Network and Internet, and click HomeGroup to launch a troubleshooter.Turn off all firewalls
Enable IPv6
Your PCs need to support IPv6 and have it enabled in order to connect to a HomeGroup: from the Network and Sharing Center, click "Change Adapter Settings", right-click your network adapter and choose Properties, then verify the TCP/IPv6 entry is ticked. Ensure also that IPv6 is enabled in the router.Check services
Press Windows + R, type "services.msc" and press Enter. Check the following services are running: HomeGroup Listener, HomeGroup Provider, Peer Name Resolution Protocol, Peer Networking Grouping and Peer Networking Identity Manager.Rejoin HomeGroup
Leave the HomeGroup, then delete the contents of thec:\ Windows\ServiceProfiles\ LocalService\AppData\Roaming\PeerNetworkingfolder – you'll need to click "Continue to" when prompted to access the LocalService folder, and AppData is a hidden folder.Give up on HomeGroup
Remove the HomeGroup from your main computer, then click "Change advanced sharing settings" and configure your network manually. Once this is done, you can then share any individual folder by right-clicking it and choosing Share with > Specific people.
HomeGroup uses multicast IPv6, specifically WS-Discovery.
In the comments you said the computers were able to ping each other, but most likely this was a ping using IPv4 addresses. An IPv6 address uses hexadecimal numbers separated by colons (not to be confused with a MAC address). First check that each computer has an IPv6 address, then try pinging using that address.
Lastly, since IPv6 is relatively new, your hardware needs to support it. As a rule of thumb, you would want to be using computers (specifically, their network adapters) and a router from 2008 or later.