If your account went from consistently gaining followers to suddenly losing followers permanently from one day to the next, your account likely got shadow banned. Also, monitor the views, comments and likes. All of these metrices would indicate that you are shadow banned. In fact, the simplest explanation would be: If you can just log in into your account but can't do anything else and if you get the feeling of having a banned account with the only exception that you can login, unfortunately, you are shadow banned.
In order to avoid it, you must make use of proxies - mobile-elite proxies. Also, there is nothing to worry about if you are shadow-banned. Just stop using that account for a few weeks and your shadowban would be lifted.