html5 canvas movie will not play when Bitmaps are present on timelne

I using Animate cc 2020 to create interactive animations in html5 canvas format. If I create a simple animation by drawing objects on teh screen the movie plays back perfectly. But then I add a movie clip or text or graphic from the library and the movie just shows a blank stage when I try to test it or play it in a browser. If I remove the symbol from teh timeline it plays perfectly. I am desparate for help as I have several projects to do before the end of the year.