Are you receiving a specific error message when attempting to update your Barclays account? Any additional details you can provide me will help to ensure a timely solution.
In the meantime, you can manually update the bank account. It helps refresh the connection between QBO and your financial institution. I'll show you how:
Go to Banking from the left menu.
Choose the blue tile for Barclay.
Click Update.
If it doesn't work, the issue may be on the bank’s end. I'd suggest logging into your bank's website to check if there are alerts that need your attention.
If you're still unable to download new transactions, as a workaround, you can manually bring the transactions into your QuickBooks Online using a WebConnect file. You can get the detailed steps in this article: Manually upload transactions into QuickBooks Online.