There are several reasons why you might not be able to print to a homegroup printer:
The printer is turned off.
The computer that the printer is connected to is turned off, asleep, hibernating, or has left the homegroup.
For information on changing power saving options, see Change, create, or delete a power plan (scheme).
Another member of the homegroup stopped sharing the printer.
Network discovery might be turned off. For more information, see Enable or disable network discovery.
The printer has a non-USB connection and must be shared using Devices and Printers in Control Panel.
An incorrect printer driver is installed. Printers must use the correct driver for the type of computer they are connected to (x86-based or x64-based). Many printer drivers can be downloaded automatically from Windows Update. Downloading and installing drivers from Windows Update might take up to 30 minutes. Drivers are also available from the printer manufacturer’s website. For more information, see Find and install printer drivers for Windows 7.
Sometimes, restarting your computer or leaving the homegroup and then rejoining it might help you access printers in the homegroup.