Video created as Storyline output has blank start screen when used in Rise multimedia block

Same as Errol. I  just insert a blank slide in the first position of the new Scene — no animation on the slide, no Transition between this slide and the next, no Audio, and no Video. Like Errol, and depending on the project, I'll either insert a relevant photo from the Content Library, or I'll take a full-size screen shot of the beginning of the video, save it as a .jpg or .png and insert it (so it gives the illusion it is the beginning of the video). I then drag the Timeline on that first slide to something very short, like 0.5-1 second, and apply the Slide Triger "Jump to next slide | When the timeline ends on this slide." Then publish and add to Rise. This works for me.