2500 - Invalid Reference Id : Line.SalesItemLineDetail.ItemRef

Greetings, @dr-rashel-offici. 

Thanks for the detailed reply and for giving the exact error message. I'll ensure that you'll be able to sync your sales.

Invalid Reference Id indicates that an item or account is inactive.

Did you use a third-party app to sync your sales? In the meantime, you can follow these steps to make your items active.

Here's how to do it: 

Reactivate products or services:

1. Go to the Gear icon menu, then select Products and services.
2. Click the Filter button.
3. Set the Status to Inactive.
4. Click Apply. 
5. Check those items with the (deleted) tag, then click Make active. 

If the error persists I would recommend checking it and seeing what's causing the errors. You'll want to contact third-party app support if you need help with this.

If you also need to connect your bank account to match or categorize your transactions, you can check this article for a guide: Connect bank and credit card accounts to QuickBooks Online. 

Don't hesitate to comment below if  you have more questions about syncing your data in QuickBooks Online. If you have any other concerns, please add them to your reply.