Introduction
In Azure DevOps, Project collection Administrators are members of the application group who can perform all privileged operations on the Team Project Collection. Ideally you should have more than one project collection administrators to maintain your project collections in the organization.
If your Azure DevOps Organization has only one Administrator , Azure DevOps shows an alert “Your organization only has one Project Collection Administrator. To reduce the risk of losing admin access, you may want to add additional users to the Project Collection Administrators group.”
Fig: Azure DevOps - One Project collection Administrator Alert
To be on the safe side and get rid of this alert, click on Add Administrators > add another account > Save > Alert message will disappear on refresh.