Why some events are not being synced?
There might be two reasons that some of your events are not being synced:
Events might be outside of the syncing timeframe
By default, you can sync events for up to 15 days, but can update that to up to 1 year.
To change the value, go to you account settings, and then select "Sync Settings" > "Syncing timeframe":
Events might have been created before your first sync
By default, when we sync a Notion database and Calendar, Notion Automations do not add existing entries (to avoid having any redundancy from previous workflows).
You can change that setting on "Sync Settings" > "Sync Notion entries that were created before the first sync":