No user when adding user or group to Application (IAM/applications)

Hello.

Please search by entering the display name of the user in IAM Identity Center as described in the following document.
https://docs.aws.amazon.com/singlesignon/latest/userguide/assignuserstoapp.html

In the Assign users dialog box, enter a user display name or group name. You can specify multiple users or groups by selecting the applicable accounts as they appear in search results.

I checked on my AWS account, and was able to add a user by searching by the user's display name.

It appears you're encountering an issue where no users are displayed when trying to add users to your application. This is likely because you need to first set up AWS IAM Identity Center (formerly AWS Single Sign-On) and add users to your Identity Center directory.

When you create a new application that uses IAM Identity Center for authentication, the application doesn't contain any users by default. You need to:

1. Set up IAM Identity Center for your account
2. Add users to your Identity Center directory

To add users to your Identity Center directory:

1. Open the IAM Identity Center console
2. Navigate to Users in the navigation pane
3. Choose "Add user"
4. Provide the required information (username, email address, first name, last name, display name)
5. Choose whether to send an email with password setup instructions or generate a one-time password
6. Add the user to relevant groups if needed
7. Complete the user creation process

Alternatively, if you're using an external identity provider (like Active Directory), you'll need to:

1. Go to Settings in the IAM Identity Center console
2. Select the Identity source tab
3. Choose Actions and then Manage Sync
4. Add users from your external directory

Once users are added to your Identity Center directory, they should appear in the dialog when you try to add users to your application.

Note that if you're using AWS Managed Microsoft AD, be aware that users in nested groups are not supported - only members of parent groups will have console access.
Sources
Add users to Fleet Hub applications - Fleet Hub for AWS IoT Device Management
Add users and groups to your sync scope - AWS IAM Identity Center
Assigning users or groups to an existing IAM role - AWS Directory Service
Add users to your Identity Center directory - AWS IAM Identity Center