Volvo's have lots of extra sensors.
Most cars with 'interference' engines have a cam and crank position sensor. Either one can keep the engine from starting.
The cam position sensor will be somewhere on the head, and the crank position sensor will be on the block. Either get a maintenance manual on your car, or try finding something online that shows you.
You can buy both sensors (then you will know what it looks like - which might help you find it) and swap one, and if that doesn't fix it, swap the other one. If that fixes it, you can take the other one back out and get your money back (or just keep them both in, so they are both new).
If it still won't work after swapping them both out, then your problem lies elsewhere.