Got the same problem here but for me the video did work earlier, even after packaging to android. Then to reduce the package I foolishly turned off a bunch of plugins (and might have changed some settings as well) and now the audio plays after the unreal logo and instead of video I get a white screen. The video is in the proper format as it worked earlier but now I don’t seem to remember what settings I changed that messed it up. (UE4.25).