Please check your browser Console for any errors. In order to see the browser Console you have to press Ctrl+Shift+I in Chrome/FireFox (Windows/Linux) and click on Console tab.
If everything is OK then you should see no errors like this:
Here you can see an example of a Chrome Console tab with an error:
If you see red text errors then please do a screenshot of your browser window by pressing Alt+Print Screen buttons on Windows (Click here for Mac info).
Then paste the screenshot into an email and send it to us at: firstname.lastname@example.org
You can also select all Console text and copy it to clipboard (Ctrl+C) then paste it (Ctrl+V) into email and send.
Also please send us information what browser name and version are you using.