This one is baffling to me. I imported four elements from Illustrator into a pre-formatted 160x600 Animate template. Even just sitting on one frame in the timeline, the exported animation will NOT show a background color, even if I make one myself as a layer / symbol in the main timeline. I've quit, re-started, tried making the background color on the stage the same color as well as having an actual rectangle movie clip on the stage - yet when I export it will ONLY show the other artwork elements. It simply will not show any background.
I have made sure tha the "transparent" option is NOT checked in the export options dialog. that comes up when you save. See attached image of authoring environment and what the results are like when it's exported as an animated .gif.
Note: I have been a Flash user for over 15 years, so I'm no newbie to this environment. It's never been a great tool for making animated gifs, so I was hoping the new Animate might have some better features for that. But I've never seen a glitch like this. I also tested this with multiple frames in the timeline and a stop action to make sure that wasn't the issue.
Second note: if you export a static .gif with the export options, the dark blue background does show up. So baffling.