Since yesterday, users have been reporting that they are greeted with a blank or white screen when they open the Instagram app or try to log into their account. Some users have had this problem in the past, but over the past 24-48 hours that has been an increased amount of reports on both social media and online forums. Some people have reported that you can fix the issue by logging into the desktop version of Instagram and then try to login to your account via the mobile app. If that does not work, you can force all devices to logout by changing your password through the desktop site.
Source: https://www.bleepingcomputer.com/news/software/instagram-only-showing-a-blank-white-screen-for-many-users/