I have been having all sorts of weird things happen on the browser version lately. I switched to the app version on my Mac & they all went away, sans a little loading issue the first time I tried opening it after install. I'm much happier using the app version now. Maybe that would help you as well.
Let's get this issue sorted out by doing troubleshooting steps. So you're able to see and use your dashboard in QuickBooks Online.
First, try logging in to a different private window to check if it's a cache issue or not.
To launch a private window, try out these keyboard shortcuts:
Safari: Command + Shift + N
Mozilla Firefox: CTRL + Shift + P
Google Chrome: CTRL + Shift + N
Internet Explorer: CTRL + Shift + P
Once logged in, go back to the Dashboard page and check if it's already functioning well. If it works, clear the cache of your regular browser to speeds up the web browsing experience. Using another compatible browser is a good alternative too.