Antonyms for "had a crack" could be "failed," "declined," or "refused." If someone did not attempt something, they did not "have a crack." Alternatively, if someone was unsuccessful in their attempt, they can be said to have "failed" at it. In some cases, a person may choose not to try something and "decline" the opportunity. Lastly, if someone actively turned down the chance to try, they "refused" to have a crack at it. These antonyms show the range of potential outcomes when someone does not "have a crack" at something.