Why do I only get the offline activation option when I click “Enable online licensing?”

Either you don't have Internet access or the Online License Server doesn’t use proxy settings from your web browser. You will need to configure the proxy settings manually from this page in your browser: http://localhost:30304/#/settings. Under “Connection” options select “HTTP Proxy,” in the “Use Proxy” field, enter your proxy IP address in the “IP or Hostname” field, and add the proxy port in the “Port” field. You can also use “Automatic Proxy Detection” option and the License Server will use the proxy server automatically.

Some proxies are configured in a way that they change the certificate that the OLS is exchanging with our central license server, and that's not a supported behavior. If that's the case in your environment - make sure you add an exception in the proxy's settings.