If I corrected an opening balance in bank, I deleted incorrect entry in account history and did a journal entry however when i go to reconcile beginning balance is zero?

Hello there, pauline_mason.

This can happen if the journal entry for the opening balance was not manually reconciled. This is why it shows zero when you go to the reconciliation page.

Even though you haven't started reconciling the account, you still need to reconcile the journal entry by following these steps:

1. On the left panel, select Accounting > Chart of Accounts.
2. Click the Account history link of the bank account you want to reconcile. Search for the opening balance journal entry, and select it to expand the view.
3. Under the Reconciliation status column (Indicated by a check mark), click the blank field until you see an R. This reconciles the transaction. Select Save.

I'm adding some sample screenshots below:

Once done, go back to the Reconciliation window and you'll see the beginning balance. 

I'm also adding this article for reference: What to do if you didn't enter an opening balance in QuickBooks Online.

You can reconcile the bank account after. If you have any additional questions, I'm just a post away. Have a great day!