Was your user able to see AEM when going to https://experience.adobe.com/?
In order to fix this, you would need to have the Org claim the domain, for ex: abc.com. This will require that cloud to request access via Directory Trust.
Here is a link that explains it in more detail: https://helpx.adobe.com/enterprise/using/set-up-identity.html#directory-trusting
After this is done, you'll want to change the test IDs with "@abc.com" inside the Admin console. This should resolve the user's experience.
Next, the users should log out then back in for the changes. Here is information: https://helpx.adobe.com/enterprise/using/switch-user-identity.html
>>> see section "Migrating users | Overview" >> "Adobe ID to Federated ID"
Note: If you do not see an option for "Edit identity types" when you get to that part, re-engage me to help set the feature flag to enable this.
>>> this will be in the part of the document that gives this step:
"Click ..., and select Edit Identity Type by CSV from the drop-down list."
Note: be mindful of the section on the page titled "Asset migration"
Also, check if this user is also added to the product profile for that instance
