Let me share some insights on fixing QuickBooks Online(QBO) when opening the app.
First, let's try logging out of the QBO app first and then logging back in again. This should help to isolate the issue and get you back up and running.
Then, if you're experiencing a problem while using a web browser and you suspect that it might be related, we can perform a few troubleshooting steps to identify the issue. Caching files that are either outdated or corrupted may cause issues with your web browser. To start, you can open an incognito window on your QBO account. Depending on the type of browser you're using, you can refer to the following keyboard shortcuts: