AlertMedia Provisioning Error while Verifying if the User Exists "Multiple users found by userName. Expected 0 or 1 results but was 2"

AlertMedia provisioning flow fails with the following error visible in the Okta dashboard:

An error occurred while assigning this app.
Automatic provisioning of user <username> to app AlertMedia failed: Error while verifying if user <username> exists: Multiple users found by userName. Expected 0 or 1 results but was 2

• AlertMedia
• Provisioning
• Error

The cause of this issue is that there are multiple users found by the same userName on the AlertMedia side. 

1. Please open a support case with AlertMedia support. They will be able to assist in checking whether there are multiple users with the same userName and in fixing the issue.

2. After confirming that the issue is fixed on the AlertMedia side, attempt the user provisioning again. Go to Okta Admin Console and navigate to Dashboard > Tasks. Any failed assignments should appear under Tasks.

3. After identifying the failed task for the user that should be retried, click on Retry Selected.