The problem I see a lot in people who have a hard time debugging is continuing to assume all of their base assumptions in the face of a bug. You've hit the bug

The problem I see a lot in people who have a hard time debugging is continuing to assume all of their base assumptions in the face of a bug. You've hit the bug because of assumptions, so ask yourself: which one of those assumptions, when changed or challenged could produce the outcome you're observing? Sometimes those assumptions are as basic as "I typed everything correctly" but other times they're more nuanced like "I assumed this library only throws when getting a transport error not an HTTP error code". IMO, it's a muscle you exercise. You build understanding in your problem space and get more skilled at identifying likely culprits for bugs. Early on though? It's a lot of asking, seeking and brute forcing. Also, print statements or use a debugger to confirm assumptions. (I'll be honest, I rarely bring out a debugger unless a print based workflow is time consuming enough to justify remembering everything about the debugger).