There are times that the browser is full of frequently accessed pages, thus causing some unusual responses to the system. You can fix this by performing some troubleshooting steps. You can start by logging into your QuickBooks Online (QBO) account using a private browser (incognito). Here's how:
Press Ctrl + Shift + N (Google Chrome)
Ctrl + Shift + P (Firefox)
Control + Option + P (Safari)
Once signed in, go to the Banking tab. If you're able to open the said page, return to your default browser and clear its cache and cookies. This will refresh the system and remove older data which causes viewing and performance issues. However, if the problem continues, I'd recommend using other supported browsers.
Through the Banking tab, you're able to add and match your online banking transactions to the existing entries in QuickBooks. This way, you can keep your accounts accurate and monitor your real-life transactions. You can learn more about this by checking out this article: Categorise bank transactions. It also contains information about excluding personal or duplicate ones.
Additionally, I'd also recommend reconciling your accounts every month. This is to effectively monitor the growth of your business and making sure your books are accurate. You can check out this article for the step-by-step guide: Reconcile an account in QBO. It also includes instructions about editing completed reconciliations.
Please tell me how it goes. You're always welcome to comment below if you have other concerns or follow-up banking inquiries in QBO. I'm just around to help. Take care always.