Instagram does not redirect the user to the app after sign in

We are building an iOS app where users are asked to sign in with Instagram.

The flow is as follows:

1. we open an Instagram login page in a web view,
2. user inputs his login and password,
3. then in most of the cases he is asked to verify his account by getting a code by email or phone and entering it on the next page,
4. after doing so, Instagram app opens in a web view and does not redirect to the app.

I saw a similar issue here, but did not find it usefull.

Maybe you have faced such an issue before and can somehow help.

Thanks!