Be sure you check your browser settings and ensure that you have javascript enabled. (Java is NOT the same as javascript, despite the similarity in names!)

Have you restarted your computer? I hate to give the stereotypical "turn it off and turn it back on again" advice, but that often helps with this issue.

Well, if it had been disabled, it would. ;) That is the cause of this issue. But my next suggestion is to try restarting your computer, if you haven't already tried that.

Third thing to try is (temporarily) disabling ALL addons/extensions you're running in your browser, because there are quite a few that can interfere with site function.

Are you using any CustomCSS?

Man, these are being stubborn!

How about you, any CustomCSS?

This should be resolved if you do a hard refresh :)