SSL server certificate rejected ("An SSL error has occurred and a secure connection to the server cannot be made.")

We’re getting more and more reports from user experiencing this issue in the app in production. The app is using MongoDB Realm and the users are on iOS.

We’ve already tried to change the iOS specific settings regarding SSL, i.e. setting NSAppTransportSecurity > NSAllowsArbitraryLoads to true, but that didn’t change anything.

This error happens in various calls to the MongoDB Realm backend: logging in, logging out, client reset, etc…

Any idea on how to solve that?