When a browser stored a lot of caches, it could cause problems like bringing up the data to your account or latency issue. As an initial step, you can press the F5 key on your keyboard to refresh the page.
If you're still unable to access the URL, let's open your account in a private window. Simply press the following keyboard shortcut keys:
Press Ctrl + Shift + N (Google Chrome).
Ctrl + Shift + P (Firefox).
Control + Option + P (Safari).
From the incognito window, access the URL from there. If you're able to open the link, go back to your regular browser and clear its cache. It could be that there's an issue with QuickBooks and the browser that you're using.
If the problem persists, I'd suggest following the steps below in reclassifying your transactions in QuickBooks Online.
Click the Accountant Tools and choose Reclassify Transactions.
From the Account types drop-down menu, select Profit and Loss to see income and expense accounts. Or select Balance Sheet to see your asset, liability, and equity accounts. From the Account list, select the account with the transactions you want to change.
Use these type, class, customer/supplier, and modify filters to filter the list. Tip: You can also select Accrual to see all paid and unpaid transactions or Cash to see only paid transactions.
Tap Find Transactions.
Tick the check-box for each transaction you want to change. Before you move transactions to Accounts Receivable or Accounts payable, make sure there's a customer or supplier. Don’t leave these fields blank.
Select a new account to move the transactions to from the Change account to drop-down, or a new class from Change class to drop-down.