I've started having the same issue yesterday as well, noticed few times before but it was happening 'sometimes', now it happens all the time. Only workaround is to switch to implicit oauth as @xmrcivicboix suggested
Instagram has fixed the issue, at least it appears to be the case to us.
Are you sure about that? We're still getting this error.
at the time of my last writing, i was sure as all accounts are working fine. But today, it started acting up again. Now I had to change up to different wifi to login with Instagram.