"Image Upload" button not drawing

Just started with Sitefinity 5.4 but am obviously missing something very basic. When working in the backend on the production site selecting "upload image" from any of the image libraries shows a blank screen with a silver panel but nothing else, no buttons or writing. Can't do anything but use the back to images hyperlink to get off the page. 

It does work on the local development machine but not on the hosted production site.

Has anybody else seen this behaviour and know how to fix it?

EDIT: ........DUH, never mind, problem was mine and I've corrected it.