So on my previous phones (moto's) I can look as far back as 2017 on google calendar for events and so forth. On my 4a (4g) got in Dec 20' once I go to say 2019 and older I see nothing. I can see things are being synced. Am I missing something?
Try clearing the app cache/data from the Google Calendar app in Settings>Apps, then let it resync and see if the problem persists.