Your issue may relate to the overloaded Instagram server. The principle is that for each time you unfollow, our app will request the Instagram server.
If there are too many requests to the Instagram server, for example, unfollowing 100 accounts, Instagram will stop answering you. How long the Instagram answer you depend on how much it trusts you again. The solution to this situation is to refresh the app and do not run activities too fast.
Please try to log out of the app, then refresh the app background first. After that, please try to log in and wait until the app complete to load all your data then continue to unfollow people.
Overloaded server is one of the most common issues you can encounter when using any apps like Followers+ for Instagram. Thank you so much for understanding.