I have reconciled my cash on hand account and then did the undo reconciliation manually! but now the balances in Sub account of Cash on hand account are not matching!

I'm here to make sure the balance on your Cash on-hand account's sub-account matches, @h-azad.

When the balances on the sub-account of your Cash on hand account didn't match after undoing a reconciliation, you'll have to manually check which transactions cause this issue. To do this, open both the Cash on hand and subaccounts history. Here's how:

1. Go to the Accounting menu.
2. Select Chart of Accounts.
3. Find either the Cash on-hand account or subaccount first, then select Account history under the Action column. 
4. Click the transaction you want to check to expand the view.
5. Make the necessary updates.
6. Select Save. Repeat as needed.

Once you're done, reconcile your accounts again to correct the specific reconciliation period. I'd recommend reconciling them every month to keep your financial data updated.

Additionally, I've included this article to further guide you in reviewing your accounts and making sure the amounts match your real-life bank and credit card statements: Reconcile Workflow in QuickBooks.

Please let me know if you have other reconciliation concerns or inquiries about managing transactions in QBO. I'm just around to help. Take care, and wishing you continued success.