How is it possible that the beginning balance on the reconciliation page is different than the ending balance on my last successful reconciliation and how can I fix this?

Thanks for the response, Carneil_C.  Sadly, I've already done what you've suggested.  The beginning balance for the period I'm reconciling exactly matches the last successful reconciliation AND the beginning balance on the bank statement.  When I click the "We can help fix this" or whatever button, the reconciliation log shows nothing.

Now for the back story...I'm trying to correct some incorrectly done reconciliations from 2021 (which I recently discovered...I know that's really bad).  I've created myself an accountant account and used the Undo option to remove reconciliations back to that point (when I had incorrectly entered a transaction and then later incorrectly reconciled it - I'm a volunteer treasurer for my church who is trained in engineering not in finance/accounting and I was doing lots of self-teaching).  After a call with the QBO support team (who gave me almost nothing helpful), I opted to try the July '21 reconcile again but this time I unselected all the transactions QBO pre-picked for me.  I then manually selected each one that was on the bank statement.  This revealed 3 transactions that were not on the list of possible transactions to reconcile.  I checked them and found they had been (incorrectly) reconciled in a prior period. (Note, I reconciled all of 2021 one weekend in Dec '21 once I realized the reconciling was a thing.  I clearly hadn't done those properly.) So, I rolled back another month's reconciliation.  Repeated the process and found more transactions not available for selection for that period (for the same reason).  I repeated this until I had removed all the reconciliations I'd done myself and to the point where the last completed & successful one was done by my predecessor.  It is at this point, QBO was telling me that I couldn't start because my beginning balance was wrong (north of $17K wrong) yet showed nothing in the reconciliation log.  I'm totally baffled. If the Undo option on reconciliations really does so completely, my engineering brain cannot fathom how I'm facing this mess.  Any further insights are appreciated.  The upside is that I figured out how to properly execute reconciliations so if I could just get to the point where I could resume doing the last 24+ months' worth of them I'd be golden.  I'll toss another weekend at catching up.