ADDITIONAL SOLUTION: What I found after much frustraion is I had to go to my default app Calendar, press the 3 lines in upper left corner, under Calendars - press the little down arrow beside your google calendar and you will find several sub-calendars, ensure that all the correct calendars are ticked. In my case I had subscribed to an external calendar (chiro appointments) through my google calendar, so this had created a new sub-calendar within my google calendar. I had to go in as above and tick this new calendar so that it would sync with my samsung default app calendar. Hope this helps you.
... View more