How do I network Denon AVR 2113CI with PC?

Check the speakers.
http://electronicshelponline.blogspot.com/

If the DENON has an HDMI output, and your TV has an HDMI input, then use a HDMI cable. Then, use the TV's remote-control to select "source" (or "input") as 'HDMI 2' or 'HDMI 3' (assuming that you have been using 'HDMI 1' to watch TV).

If this is a video problem, try different video connections (i.e. HDMI, Component, Composite, S-Video) to isolate the problem

is your cable hooked up via hmdi cable? the zone 2 will only work with an analog signal

Is thereany sign of power? relay click or anything?

ok to first check the obvious things. you are using the standard remote that came with the unit i can assume, and you've tried a different fresh set of batteries, and there is nothing blocking the receivers remote sensor or the remotes output sensor. If you have a smart phone there is an app for Denon AVR's that allow you to use your phone to control the unit assuming you also have a home network that the AVR is connected to.
If everything else works with the app you may just have a faulty remote, hard to test without trying it on another persons same model AVR

re-install sound drivers

you need another reciever/amp to power that sub, because that denon reciever is designed for a powered sub,. if you have another old reciever/amp laying around, you can connect the sub out from the denon into an auxillary input of any old reciever/amp, (switched to that input) with speaker wires from old reciever/amp to the passive sub

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Can you update the firmware on the amp as this could also affect the connection between the players.