MC Next: Error with Push/InApp Test

Good afternoon everyone, hope you're doing well.

I'm currently having trouble running Push and InApp tests in Marketing Cloud Next. Salesforce informed us that the contact needs to be mapped to the Contact Point App DMO.

We did the DMO mapping correctly, but even so, the users still aren't populating in our DMO, and we haven't received any of the test messages. Do you know if there is a mandatory field that needs to be filled out? Or if we might have missed a configuration step during the process?

Note: The goal is to successfully perform these send tests (push and in-app) in Marketing Cloud Next. If you have any real-world scenarios, documentation, or use cases to share, it would help us a lot. 

Thank you!