You can verify if the API Server was installed correctly and is running by navigating to the following URL in your browser:
[SERVER]/[VIRTUALROOT]/onbase/core/healthcheck
Replace [SERVER] with the name of the server that is hosting the API Server. Replace [VIRTUALROOT] with the virtual root of the API Server. In a default installation, the virtual root of the API Server is ApiServer.
If a blank page is displayed without any kind of error, the API Server is currently running.