QuickBooks Online (QBO) and QuickBooks Online Payroll (QBOP) uses the same URL (qbo.intuit.com). Just make sure to enter the correct credentials for your QBO account.
If the same thing happens, try signing into your QBO using a private browser (incognito). This will help us check if this is a browser-related (cache and cookies) issue.
Here's how:
Press Ctrl + Shift + N (Google Chrome).
Ctrl + Shift + P (Firefox).
Control + Option + P (Safari).
If it's successful, return to your default browser and perform a clear cache to refresh the system. However, if the issue persists, try using other supported browsers.