If you have Google Chrome open up Developer Tools ( right click -> Inspect ) and check if there are any red ( javascript ) errors in your console:
https://developer.chrome.com/devtools/docs/console
Firefox has a similar layout if I’m not mistaken. Report back with the errors
just registered to say I have exactly the same problem.
the problem was “Yoast SEO” plugin
after deactivated it everything working fine
yes I get this javascript error “Uncaught Error: no such method ‘instance’ for autocomplete widget instance” and I haven’t “Yoast SEO”
I track this problem and I found when deactivate this plugin “DesignThemes Core Features Plugin” it work fine but this plugin is very important to my site .
also in my frontpage I get many errors
Failed to load resource: the server responded with a status of 422 (Unknown Error)
jquery.js:2 Uncaught Error: Syntax error, unrecognized expression: a[href^=#]
http://fonts.googleapis.com/css?family=Roboto%2BSlab%3A400%2C700 Failed to load resource: the server responded with a status of 400 (Bad Request)
Sorry but I resolve the problem by the quick resolving way downgrade to 4.2.2
