Hi kncrendering,
There are two options on how to resolve this issue. You can undo the reconciliation (which only your accountant on QuickBooks Online Accountant can do), or you can ignore the discrepancy message and proceed with the reconciliation. When you complete your reconciliation there will be a discrepancy, but select Finish Now, and QuickBooks will automatically create an adjusting entry to rectify the discrepancy.
You can then proceed with the reconciliation after, with the correct opening balance.
Bonny