“What can I do?”
Simply put you can try to fix it.
If you would like us to help you troubleshoot the circuit we need clear photos and measured voltages of all transistors labeled by which Q and which lead. This circuit has been available for 8 years so you can be assured the circuit board is just fine. There is nothing wrong with the components you mentioned that I see.
2N4125 and 2N3906 are both PNP transistors with similar properties and lead orientation.
We will need the required troubleshooting info that is requested for all build issues and we will try to help.
If you do not understand voltages etc. Here is a GUIDE See pages 8-9.