The phrase "gotten hang of" implies that someone has learned or become proficient in a particular activity or skill. The antonyms for this phrase could be "confused," "struggled," "failed," or "floundered." These words suggest a difficulty in understanding or performing a task, indicating a lack of proficiency or knowledge. Additionally, "unfamiliar," "novice," and "inexperienced" are other antonyms that describe someone who has not yet become comfortable or skilled in a particular area. It is important to note that these antonyms do not suggest that someone cannot eventually master the skill or activity, but rather that they are currently struggling with it.