When the Google Sheet Sync is not starting automatically and is stuck in planned or past due, try the following things:
Check if WP-Cron is disabled
Go to the LPagery Settings to the Google Sheet Sync Section and check if there is the following message shown:
If this is the case, please enable WP-Cron or check you server cron configuration. You might ask your hosting about this.
Start the Sync manually
Go to Manage and click "Sync Now" at the Three-Dot-Menu of the corresponding Page Set. The Sync should start in a few seconds.
Please note that the LPagery Google Sheet Sync relies on WP-Cron and if the sync does not start correctly, it might be an issue with the Cron-System in your wordpress instance. A great plugin to debug this is https://wordpress.org/plugins/wp-crontrol/