Can't open dropdown menu

That typically happens when a plugin on your site loads a second, older copy of jQuery by adding a <script> tag instead of using the wp_enqueue_script function. Try disabling plugins one at a time to work out which is the guilty party, then make the necessary changes to remove its jQuery reference.

@kota1111 the version of jQuery that site loads is quite old; you can try overriding it for WPtouch by switching admin mode to Advanced (WPtouch > Core Settings), then enabling “Use jQuery 2.0 in themes”.