Couldn't enable an automation

You should post a screenshot of “expanded” configurations of Triggers and Actions, this view doesn’t provide any information that might help people here with the problem.
Also when you say you cant enable automation, do you get any error or? That might also be useful.

Here is the expanded triggers and actions. No error message found.

and here is the message that I see when I tried to enable automation

Personally I haven’t used this action yet, but my guess here is that it requires you to enter end date also, and that is why it is thinking your configuration is incomplete (which kinda makes sense since it wouldn’t know when your event will end otherwise).
I don’t see anything else that could be problem.
Did you manage to run test on action part also?

Your screen capture doesn’t show the rest of the configuration screen below the date/time info. Have you added a title for the event?