Be sure the L and R switches are set properly on the wireless receivers.
On each receiver, be sure the L/R (left/right) switch is set appropriately. One receiver must be set to Left and the other to Right; the receivers will not work if they are set the same. Toggle the switch of the receiver to be sure it is fully set to the L or R position.
Reset your system
A reset is used to correct occasional product issues. It is not something that a product should require repeatedly. For more info, see Resetting your product
Disable any "channel bonding" or "40MHz mode" on the wireless router.
The "channel bonding" mode available on 802.11n wireless routers allows for the use of more bandwidth than Bose system is able to filter out. Turning off this mode or selecting the 20Mhz mode will allow the system to work around the Wi-Fi channel in use by the router.
Try connecting the rear speakers with wired connections.
Wireless interference in your location could prevent the wireless receivers for the rear speakers from working properly—especially if the receivers or sources of interference cannot be positioned to avoid interference. In these cases, you can plug in your rear speaker cables to the system console.