I know exactly where you're coming from.
My girl Abby, who will be 5 at the end of May, also came from the shelter. She has very, very little interest in any toys. We have tried squeaky toys and toys that make crinkly paper noises. We've tried rope for tugging and rubber balls and Cuz's and everything in between.
At this point, she will play with balls. We have a big orange basketball that we play with and a smaller blue one. Both have been "popped" but tend to re-inflate throughout play. It does take some work getting her interested in it. Usually, we'll let her run around a bit first, and then DH and I start playing "soccer" with the ball. That's when she gets interested and starts chasing the ball. When she "catches" it, she'll shake it and run around with it, then bring it back to us and wait for one of us to kick it or pull it away from her to chase.
But that really is the extent of play she does. And she only does it outdoors and if we play with her. (I have to say, playing soccer with DH while there's a dog chasing the ball is quite challenging...) Sometimes she'll get interested in plastic water bottles or plastic milk jugs, too. I think it's the "crunch" sound they make when she bites down on them.
The other thing she really likes is the Kong and I use it very sparingly because I want it to stay "special".
What I would do in your situation is, well, exactly what we've done. Try loads of different things and in different situations. Try playing with her or getting other family members to "show" her how to play.