Most of the time, you'll only need to clear your browser's cache to fix unusual behaviors when using QuickBooks. There are instances wherein the stored cache can cause small issues if it gets full of outdated files.
First, let's check using a private browser. Depending on your browser, here's how:
Google Chrome: Ctrl + Shift + N
Mozilla Firefox: Ctrl + Shift + P
Internet Explorer: Ctrl + Shift + P
Safari: Command + Shift + N
Sign in to your account using the shortcut keys and check if you're able to view your dashboard. If it works, you can go back to your regular browser and clear the cache.