Did the rendering process fail? Or didn't it show up at all?
If the rendering failed: Did you toggle the first parameter for before export?
If it didn't show up at all: Some times the thingiverse site is realy busy and I experience issues with all customizer applications. (One alternative would be to download openSCAD and render the sourcefile locally)
If the 'Oh no!' error shows up: Try to clear your cookies or use a private browser session, then it should work!