Try the following
Is it reasonable to assume your router requires password / ssid to secure internet access ?
Due to age of this device,
(1) Lower / disable current router security settings
(2) connect device directly to modem. ( softest, easiest way )
This may require you to disconnect modem from router, reset your modem then connect cable direct between modem and DTR 40.1 device.
When completed, the Modem ( and Router ) may need be reset, prior to re-connecting network
Firmware update information link ( from manual )
Go to "7-6. Firmware Update" menu.
Note that the Firmware Update option will be grayed out
for 30 seconds after AV receiver/controller is turned on.
( system attempts internet link for approximately 30 seconds ? )
Not outputting Sound ( trouble shooting ) link
Hope this was helpful