If your flying lead lash-up gave you good results, then your problem is likely to be a result of your rework for the permanent solution. This could be directly from the changes you deliberately made - or by something incidental, such as the solder bridges you mentioned or accidentally yanking on a wire too hard to damaging something on the PCB.
First thing I would check is whether other sources produce output - just to make sure the amplifier is actually working. If not, then you may have dislodged a wire somewhere (hopefully) or damaged something which would need to be found (hopefully not).
If the amplifier is working, I would next check the "headphone" jack... Is it stereo or mono? Is it switched or unswitched? Getting the pins wired up wrong could be a simple fix. Is it insulated or uninsulated - and if uninsulated, is the body in contact with electrically connected metalwork? If so, something could be shorting.
If you can't work it out, try a few tests to get an idea of what works and what doesn't and, if you can, take a photo or two of what you've done, showing the connections and solder joints. (Please make sure they are well lit and focussed - otherwise it makes it hard to see the detail.) Bring this information back here and we will see if we can spot something. No promises, but we will try.