Hi there @Steph. 

Let me provide you with some insights on why you get a notification about the Reconciliation Discrepancy. As you mentioned here, this started after you undo a reconciliation. Check what transactions were deleted and changed, then recreate and edit them. 

Here's how to review any discrepancy reports:

If anyone changes your beginning balance, you'll get a message before you start reconciling.

1. Select the We Can Help You Fix it link to open your discrepancy report.
2. Review the discrepancy report. Use it to decide if and how to make changes.
3. Before editing anything, talk with whoever made the changes - they may be intentional.

Once you know you need to make corrections, review each transaction in the report one at a time:

1. Select View to see the history of changes to the transaction.
2. Review the Change Type column. This tells you what changed. 
3. Make edits based on the message in the Change Type column:

After reviewing everything on the discrepancy report, the Total Discrepancy Difference should be US $0.00. Please verify the beginning balance in QuickBooks and ensure it matches your bank statement's beginning balance. Once you have identified and corrected any discrepancies, you can start reconciling. In case you encounter issues in the middle of your reconciliation, please review the following items.

Additionally, you can check out this article to learn how to fix issues for accounts you've reconciled in the past and if you want to undo or remove transactions from reconciliations in QuickBooks Online.

Please don't hesitate to reach out to me if there's anything else you need help with. Keep Safe!