I have had my Asus calendar since last Christmas.... yesterday my Google sync quick on my calendar. I have gone into the settings and it shows that it is synced....AND on the Google website, all my events are there...just not on my tablet. GRRRRR
Allow me to suggest a different, (and likely better) calendar app to see if it has the same problem. Get Business Calendar, (the free version), and see if it syncs.
On a side note, do you only have one Google Calendar? Some apps really don't like to see or want to see anything but the primary or possibly only 1 Google Calendar.