Hey there 
By the sound of it, styling or templates might not be getting loaded. We’ve often encountered these files being blocked by browser extensions and sometimes antivirus software.
I’d recommend first checking your browser dev tools (F12) console to see if there are any error messages being logged, and testing in safe configuration to see whether it’s happening with all modules disabled.
Of course, it’s also a good idea to make sure all your packages are updated to the latest versions.
It’s worth testing in an incognito version of Chrome (or Firefox if you normally use Chrome) to be able to tell whether it’s a browser side issue.
Hope that helps! If you see any error messages, please post a screenshot of what you’re seeing here.