AE 2019 black screen .mov

If you created the comps by selecting the footage then the frame rate of the footage that is showing is 59.94fps, which is a standard frame rate, and the footage that is not showing is 54.705. That tells me that the second video was recorded using a variable frame rate, and that is not good. Sometimes you can force variable frame rate footage to a fixed frame rate by opening up the File/Interpret Footage/General tab and just entering a standard frame rate. Other times, you need to drop the footage into an encoder like the Adobe Media Encoder and render a DI (digital intermediate) making sure that you pick a standard frame rate by using one of the presets. The best way to avoid this problem is to use an app like Filmic Pro on the mobile device to lock in standard frame rates. It is also a very good idea to stick with standard video frame sizes. Until you become an expert in video standards, frame rates, and frame sizes, you should only use the standard presets.

One other point. It is almost always a waste of bandwidth to shoot at any frame rate higher than 29.97 in NTSC countries like the US or 25 in PAL countries (50Hz power). This is especially true if you are trying to do animation that is going to require you to set keyframes or make adjustments on every frame. Almost everything you see on TV or the Web is 29.97 fps and anything above about 24 fps is going to look very smooth when played back in real-time. Cartoons (Buggs Bunny) are animated at 12fps and they look pretty good.

Let us know if forcing the footage to the nearest standard frame rate fixes the problem.