I am looking to transfer come this Spring or Fall of 2017. Can I retake the ACT?
I am looking to apply to University of Miami. I applied as a senior in high school, and I was accepted, however, I did not get enough aid. So I am thinking this may help?
Perhaps you should ask them if it will help before you waste time, money, and effort.
^ This. The SAT is a test for HS students. You would need to ask the school if they would even consider a test taken while a college student. And any aid that you would have received as a potential incoming freshman is off the table now that you would be a transfer. It seems the school does have transfer aid but at much lower levels than incoming freshman. http://admissions.miami.edu/undergraduate/financial-aid/scholarships/transfer-students/index.html
That’s what I was sort of getting at… I wanted to know if anyone has had a similar transfer experience with the school because I know some schools do not look at these tests taken after high school. 
Transfers typically are evaluated on their college transcripts. You should check out the admissions website at UF to get the details. There should be an information section for transfer students.
Many colleges that require test scores for transfer applicants accept test scores taken while in college, e.g., Northwestern, Yale, UChicago, Stanford, Brown. However, some do not. UMiami requires test scores from transfers if you are applying with less than 30 semester hours, but UMiami fails on its site to tell you, one way or the other, whether tests taken while in college are acceptable. Thus, if you want to detemrine the issue you need to contact UMiami.
Note, you also need to look further into financial aid with UMiami. Colleges as a group are typically far less generous with scholarships, or need-based financial aid that includes grants rather than loans, for transfer applicants than they are for freshman applicants. Transfer applicamnts add nothing to their stats for US News or other rankings, and thus colleges do not treat high caliber transfer applicants as something they should recruit with offers of money. In other words, your belief that a higher test score (even a perfect one) might help on the financial side may be misplaced even if UMiami accepts test taken while in college.