Thanks for sharing your concern with us. I want to make sure this is taken care of.
There are few possible reasons why balances doesn't match in QuickBooks Online (QBO). Among these are the following: There are outstanding transactions, new transactions for a connected account, duplicate transactions, edited or deleted transactions and credit card account.
Let's try checking if there are outstanding transactions that may cause a mismatch. To do this, just customize your bank register to sort it by date, and compare the recent transactions to your bank account.