As per title, all my Google contacts' birthday events are gone. The specific calendar is enabled, and in fact I can see all the birthdays as normal, but only up until the end of June 2020. After that, most of them are gone. I can find one or two if I go forward many months, but all the ones in between (which are correctly showing in Google calendar itself) are just not there.
I am using a Galaxy S8.
Same issue encountered using the stock calendar app on my Galaxy Note 10+. Those with birthdays August onwards stopped showing. Been using Samsung phones for 10 years now and this is the first time it has happened.
It's a Google Calendar issue. On a PC log on your Google Calendar, next on the left side of the page click on "Other Calendars" > + > "Browse the Calendars of Interest" > under "Birthday" select "Your Contacts"
Now on your mobile calendar app, under your Google account activate "Birthdays" and then sync your calendar app in your mobile.