Hello, everyone! This is Alex Poter, 6 years experienced certified technician in QuickBooks support services. To resolve the issue check the validity of QuickBooks error 404. It simply indicates that the web page you’re trying to access is not found on the server. Thus, try these key shortcuts in incognito mode: Google Chrome: press Ctrl + Shift + N; Mozilla Firefox: press Ctrl + Shift + P; Internet Explorer: press Ctrl + Shift + P; and Safari: press Command + Shift + N. if it works, clear cache in the browser and try again.