Hi Samuel,
Thanks for trying to help.
I ran WordPress admin again and watched as 4 errors immediately appeared (see below). I had previously tried in other browsers (Firefox, Edge) with the same problem, and with other users and other computers.
………………………………………………………………
ERROR 1:
………………………………………………………………
wp-color-picker-alpha-min.js?ver=1.12.1:1 Uncaught ReferenceError: wpColorPickerL10n is not defined
at wp-color-picker-alpha-min.js?ver=1.12.1:1
at wp-color-picker-alpha-min.js?ver=1.12.1:1
………………………………………………………………
ERROR 2
………………………………………………………………
jquery.reveal.js?ver=1.0.0:20 Uncaught TypeError: $(…).live is not a function
at jquery.reveal.js?ver=1.0.0:20
at jquery.reveal.js?ver=1.0.0:159
………………………………………………………………
ERROR 3
………………………………………………………………
jquery.tipsy.js?ver=1.0.0a:180 Uncaught TypeError: this[binder] is not a function
at n.fn.init.$.fn.tipsy (jquery.tipsy.js?ver=1.0.0a:180)
at Object.vp.init_tipsy (shared.js?ver=1.1:1192)
at shared.js?ver=1.1:1197
…………………………………………………………………….
………………………………………………………………
ERROR 4
……………………………………………………………………..
shared.js?ver=1.1:1134 Uncaught TypeError: vp.init_ace_editor is not a function
at Object.vp.init_controls (shared.js?ver=1.1:1134)
at HTMLDocument.<anonymous> (shortcode-menu.js?ver=5.5.1:114)
at i (load-scripts.php?c=1&load[chunk_0]=jquery-core,jquery-ui-core,jquery-ui-widget,jquery-ui-mouse,jquery-ui-draggable,utils&ver=5.5.1:2)
at Object.fireWith [as resolveWith] (load-scripts.php?c=1&load[chunk_0]=jquery-core,jquery-ui-core,jquery-ui-widget,jquery-ui-mouse,jquery-ui-draggable,utils&ver=5.5.1:2)
at Function.ready (load-scripts.php?c=1&load[chunk_0]=jquery-core,jquery-ui-core,jquery-ui-widget,jquery-ui-mouse,jquery-ui-draggable,utils&ver=5.5.1:2)
at HTMLDocument.J (load-scripts.php?c=1&load[chunk_0]=jquery-core,jquery-ui-core,jquery-ui-widget,jquery-ui-mouse,jquery-ui-draggable,utils&ver=5.5.1:2)