Make sure that the date in E2 is a real date not a date as a text string. To check whether the date in E2 is a real date or not, in an empty cell, place the formula =ISNUMBER(E2) and if this formula returns True, E2 contains a real date otherwise it's a date as a text string.
Excel treats real dates as numbers. If E2 is a date as a text string, you would first need to convert it to a real date. In F2, place the formula =DATEVALUE(E2) and this would return the underneath date number in F2 which you can then format as per your requirement.