"I don't know how to speak Spanish" should also be accepted.

the literal translation "I am not able to speak spanish" was rejected - wèi shénme?

Not sure about these distinctions. 不会 is not having the skill: "I don't know how to speak Spanish" was marked wrong. Casually 'can't' means the same thing. Strictly, 'can't'/bu neng implies some sort of inability rather than lack of skill?

Is "I can't talk Spanish" just grammatically wrong in English?

我不會說西班牙語。

"I am not able to speak Spanish." means the same in English as "I can't speak Spanish." Both should be correct!

我不会说西班牙语

I don't know how to speak spanish is correct too..... Please add as alternate answer