Thanks for visiting the Community, @anonymous-b0184c.
I'm here to help ensure you're able to enter your ending balance and date so you can start reconciling your March transactions with QuickBooks. Here's how:
There you go. You can now start your reconciliation for March. For future reference, read through this article: Fix issues when you're reconciling accounts in QuickBooks Online. It helps you learn about what are the causes of ending balance issues and their fixes in case you encounter any.
Let me know if you have any more questions. We're always delighted to help.