AWS Cognito seems to be broken (20/2/2018).
We had a user pool with users and the users list is now empty.
I replicated the issue creating a new user pool, and adding a user, yet the user list is empty.
Even the cli gives an empty list
aws cognito-idp list-users --user-pool-id <my-region>_<my_UP_ID>
{
"Users": []
}
On the existing pool, it happened to be using groups, and there, the users are shown. With a curious detail, when linking on a user that was being accessed recently, the last activity is older than a month.
It is bound to be a problem, so logged into technical support already, will wait for an answer. In the meantime maybe someone can find workarounds.