If you're unable to enable registration for an event, check the following:
- Check whether the event visibility is set to Admin only. You cannot enable registration if the event can only be viewed by administrators.
- Check whether there are any registration types set up for the event. You have to set up at least registration type before you can enable registration.
- If there are registration types already set up, go to the Event details tab and click the Edit button to enter edit mode. Now, click the Enable registrationcheck box and save your changes.