You may not be connected to the network. To connect to a wireless network, follow these steps:
Click the Network icon in the notification area of the taskbar, click the network that you want to connect to, and then click Connect. You may be asked to enter a network security key.
After you connect to the network, you can join the homegroup if a homegroup exists on the network.
Your network location may not be set to home. HomeGroup runs only on a home network. To change the network location, follow these steps:
1. Open Network and Sharing Center by clicking the Start button, and then clicking Control Panel. In the search box, type Network, and then click Network and Sharing Center.
2. Click Work Network or public network, and then click Home Network.
Network and Sharing Center
If you are on a domain network and your system administrator may have completely turned off the homegroup, you will not be able to join the homegroup.
One or more of the required services are not running. The peer network grouping and homegroup provider services must both be running. Here are the steps to check:
1. Open Administrative Tools by clicking the Start button, and then clicking Control Panel. In the Search box, type Administrative Tools, and then click Administrative Tools.
2. Double-click "Services". If you are prompted for an administrator password or for confirmation, type the password, or provide confirmation.
3. Next to the peer Networking grouping and homegroup provider services in the status bar, you should see the word "started". If you do not see the typeface, double-click the name of the service, and then click Start.