It could be that your transactions were not successfully added when downloaded from the bank.
To fix this, let's add the transactions manually. Here's how:
If the transactions are in the "For Review" you can click Add under Action column to show the transaction in the register.
If the transactions are in the "Excluded" click "Undo" under Action column, then go back to "For Review" and add the transaction. Afterwards, the transactions will appear on your register and you can start reconciling.
I've added a screenshot below for you to see it. I'll be around if you have any questions about QuickBooks.