Can not synchronize the Google calendar on Android with the web

I created an event using the Calendar app on Android 7.1.1 on a Planet Gemini.
In Gemini, the event appears as white text on a black background.
In https://calendar.google.com/calendar/ the event is not shown at all.

The Gemini is connected to the Internet.
I am using the Google Calendar application.
In Gemini, if I open the Google Calendar application and touch Menu, I do not see a calendar name with a check box.
In the menu, under PC SYNC, "PC Sync" is shown with a black check box with a white mark.
With the calendar open in Gemini, the event calendar icon has a point at the top left, instead of the bottom right.

I recreated the event at https://calendar.google.com/calendar/ and this event appears in the Android calendar application, which now shows two copies of the event.

What should I do to synchronize the events created in the Android calendar application with the calendar shown at https://calendar.google.com/calendar/?