One way to manually update the bank balance is by clicking on the Update button on the Banking page. From there, QuickBooks will download the recent transactions.
You might also check with your bank to see if they are doing maintenance. That is also one of the reason why bank's balance in QuickBooks isn't updating.
If in case you're getting an error, please follow the troubleshooting found in this article: What to do if bank transactions won’t download.
Let us know if you have any questions. We'll be here to help.