Launch Safari.
What happens if you press Command-L? Does the address bar highlight?
Just type in your new address and press enter. That should work.
If the address bar doesn't work with that shortcut, what extensions are you using?
Look in Safari's preferences/Extensions.
Click on each extension that you have enabled, and watch for any that will show that there are updates available. Click on any update choices.
The Automatic Updates don't seem to always work, but viewing each extension can sometimes trigger updates, or may show that updates are available.
Also, you could try disabling ALL extensions, Quit Safari, Re-launch Safari.
Does your address bar work with NO extensions enabled? If so, enable one at a time, and check the address bar again.
You should get this sorted out pretty quickly.