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 your 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 redundancy from previous workflows).

You can change that setting on "Sync Settings" > "Sync Notion entries that were created before the first sync":