You should be clear about what the circuit should actually do. Only if you know how it should in the ideal case, you can start to troubleshoot the circuit.
Keep the required effort for troubleshooting in mind!
Rather than spending a lot of time troubleshooting, it may make more sense to carefully rebuild the circuit.
You should be familiar with the handling and use of measurement instruments. Also, you should have experience to interpret measurement results.
Careful while Measuring
Easily you have created accidental short circuits when using measuring probes!
This not only results in wrong measuring results, but can also damage your circuit.
How do you troubleshoot systematically a circuit...?