Can't GET users created via REST API

I am working on an SSO integration for a client between their iMIS and Kentico systems. We are most of the way there in the development process, but have noticed a potential issue with the user records when they are created via the REST API. We can see them from the Users module of the Kentico portal, and we can see other users when making a GET call to the REST API, but we cannot see the users that we created via the API from a GET call. This is presenting a challenge because we need to be able to see if a user account already exists, and if so, we need to grab their ID and update their information in Kentico from iMIS.

I double checked the example in the documentation for creating new users via the REST API, and we’ve included all of the same fields. Is there a setting somewhere that we’ve overlooked? Is there another implied field that needs to be included when creating a new user?

Let me know what other information you need from me, and I’m happy to provide it.

Thanks!