The phrase "gotten on it" is an informal expression that is commonly used to indicate that someone is taking action or making progress on something. However, if you want to use a more formal or precise alternative, you could try using phrases such as "addressing the matter," "proceeding with the task," "tackling the issue," "working on the project," or "making headway." In addition, you could use synonyms for the word "gotten," such as "started," "begun," "commenced," "initiated," or "embarked upon." Overall, there are plenty of ways to convey the idea of progress or action without resorting to the informal phrase "gotten on it".