Replace the link on the speaker with a short piece of speaker cable rather than tin foil.
Make sure the balance control on the amp is set to the centre position, and only speaker B output is selected, which will allow you to move into troubleshooting.
Follow the list below until you locate the problem (You may not need to go through the full list to identify the fault)
1. Disconnect both speakers at the amplifier terminals
2. Connect the left speaker to the left terminal and see if you get sound out, if not either the speaker, cable or amp is faulty
3. Disconnect the left speaker and connect the right speaker to the left channel and see if you get sound out, if still the same result as 2 then the amp is at fault or if it now works then the left speaker and/or cable is faulty
4. Follow 1 to 3 above but this time using the right channel
Once completed (You may not need to go through all of 1 to 4) you will know exactly where the fault is, and can then concentrate on whether you can fix it yourself or take it in for repair.
Have fun
Bill