Typically events will fail to sync for 1 of 3 reasons.
The event type, such as multi-day, is not supported.
(see here for a list of event types that are not supported)
Google API issue with weekly recurring events
The authorization token has expired
Steps To Resolve Weekly Recurring Events Issue
Whenever creating or updating event recurrence to weekly from the custom recurrence UI be sure to click on Repeat on day even if it's already selected (screenshot below). Failing to click on the day results in the Google API treating the event differently and it may not sync to NetSuite as expected.
Steps To Resolve Expired Authorization Token
Please take note that both the NetSuite Admin and Google Workspace Admin are required to perform these steps.
Step 1: Log in to NetSuite and go to Setup > Custom > Celigo CloudExtend Setup.
Step 2: Once in the Setup, you may get the pop-up below. If so, just Allow Access as the Google Workspace Admin.
If you don't get the pop-up, just click on the link under Step 1 of the Setup page, and allow access as the Google Workspace Admin.
Once you've allowed access, hit Next until you get to the User Licenses tab.
Step 3: Review the licenses and make sure that the authorized users have their respective access checked and click Next then Finish.
You have now successfully re-granted the license and can now test the Calendar Sync.
To test if these steps resolved the sync issue from Google Calendar to NetSuite, you can run a Manual Sync.