I'm here to get you up and reconciling again in no time. To clarify, are you receiving some sort of error message when attempting this process? For most general issues in QuickBooks Online, clearing your browser's temporary cache files is a great place to start. Here's how you can do that:
By following these instructions, you'll force QBO to load a fresh copy of everything on the Reconciliation screen. Once you've got that cleared up, the guides I'm including below are sure to be of assistance with your reconciliations:
With all of these resources, I'm certain you'll find great success with your Reconciliation in QuickBooks. Should you need any further assistance, please don't hesitate to let me know. Thanks for reaching out and have a magnificent rest of your week.