Says the conditions allow the action — free to, in a position to. Negated (不能), the conditions block it.
框 · Frame
[subj] (不)能 [verb phrase]
觸 · Trigger
You want to say whether the circumstances let an action happen, not whether you have the skill or the permission.
序 · The move
1ask what is at stake: conditions, trained skill, or permissionis it the conditions that decide? then 能 — if it is a learned skill, 會; if it is being allowed, 可以
2place 能 (or 不能) before the verb phrasedoes 能 sit right in front of the action it gates?
3negate with 不能, never 沒能 for a present conditionis this a standing condition rather than a past attempt that failed?
能 asks whether the conditions allow it (今天不能運動 — the cold blocks it). 會 asks whether the skill is in you (我會游泳 — I learned how). The skill can be intact while the conditions shut it down: 我會游泳，但今天太冷，不能游.
能 leans on circumstance (the path is open or blocked). 可以 leans on permission (someone allows it). 這裡不能停車 says the spot makes it impossible; 這裡不可以停車 says the rule forbids it. They overlap, but the source differs.
skill mistaken for condition: 我能說中文（meaning I learned it） → 我會說中文
asking permission with 會: 我會不會進去？ → 我能不能進去？
negating a failed past attempt with 不能: 昨天我不能來 → 昨天我沒能來（couldn't make it that time）
English 'can' fuses skill, circumstance, and permission into one word, so learners reach for whichever Chinese word they met first instead of sorting which one the sentence means.