Have you tried putting the system in your living room and seeing if it works from there.
If you can get it working from there you may be able to figure out which inputs go from the livingroom to downstairs and from the living room to the roof speakers. Once that is figured out run a cable between the two sets of jacks in the living room and plug your reciever in downstairs.
The thing you need to figure out is which which jacks connect to which jacks. So start by making a diagram of all your jacks and then use a portable speaker with your reciever and plug one in on one end and one on the other and slowly map out what is hooked up to what. It is a rather painfully slow process depending on how many jacks are availalbe.
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