You have installed your Nexus Repository 3 Professional license and are trying to use the repository health check search extras Component Info tab by searching for or using the Browse Index tab for a repository. After selecting an open source component, and then the Component Info tab you receive a message stating Error accessing Sonatype server: Professional license is required for access to this data.
The Repository Health Check search extras features rely on running at least one successful repository analysis after the Nexus Repository 3 Professional License is installed.
In your repositories list, click the Analyze button on at least one Proxy Repository containing open-source components. When the analysis is complete, the Component Info tab should start displaying data as expected.