The hardest part of problem-solving is "Perceptual Narrowing".

You pick something that appears to be the problem and doggedly go after that until you're exhausted and making no progress.

The way to do this is to be sure -- absolutely sure -- you really understand the problem. "Solving the Right Problem" is the most important part of problem-solving.

Sometimes they call this "thinking outside the box". "The box" is a narrow viewpoint that may not include the real, fundamental problem. Thinking outside the box is to look for the right problem to solve.

There are numerous books on strategies for avoiding the narrowing that goes with premature focus on the wrong problem.

Mostly the trick is to identify what the real outcome is supposed to be. Then figure out what blocks that desirable outcome.