Napoleon underestimated Gibraltar and sea power

Why did Napoleon never take Gibraltar?

Once Britain was established there it was extremely difficult to remove, and Napoleon compounded the problem by failing to recognize Gibraltar's strategic value.

British possession became very hard to reverse after the Great Siege of Gibraltar. Napoleon did not regard the position as valuable enough to make its recovery a priority. That judgement reflects a wider failure to understand sea power and the leverage of a naval chokepoint. Gibraltar was therefore both a fortress problem and a strategic-perception problem.