Is it possible to re Sync the prior years transactions from Quickbooks self employed to Quickbooks ONline?

Yes, @herbiewalbanker, it's possible. Let me share some information about syncing transactions from QuickBooks Self-Employed (QBSE) to QuickBooks Online (QBO).

Before doing so, can you tell me if these transactions were previously synced to QuickBooks Online?

If you're switching from QBSE to QBO, you can easily move your data to the online version. If you plan to connect the same bank accounts you used in QuickBooks Self-Employed, you don't need to move any transactions. Instead, follow the steps to connect your accounts. QuickBooks will automatically download several months of recent transactions. The Online Banking feature saves time and avoids importing duplicates.

For more information, check out this article: Switch from QuickBooks Self-Employed to QuickBooks Online. 

Once your transactions are in QuickBooks Online, go to the Transactions menu, then select Bank Transactions. Follow the steps to review and categorize your transactions.

Drop your comment below if you have other questions or concerns about moving transactions to QuickBooks Online. The Community team is always around to assist.