I was working on a 10 second video with multiple layers, and I got to my last clip but when I added a transition layer my screen turned black (see attached image) and no layers show visuals. The audio still works, and I've cleared my media cache multiple times but nothing has worked.
I'm not clear what you are saying. all i say is an MP4 file at the top of your stack, which is of course an opaque layer with not Alpha channel. if it is supposed to serve any function beyond just sitting there, you have to set the relevant options or apply effects. It seems you are not understanding something very basic here, It's just not clear what you actualyl mean based on yopur lack of info and awkward description.
the mp4 file is what I'm using for sound, I have maybe 40+ layers and they all have transitions on them. I'm not concerned at all with the mp4 file as I'm able to see that if I select it, what I'm trying to see are my other layers.
I believe the answer to why your screen turned black is because you do not have transparency enabled.
I've also restarted twice, moved my clips to a new composition and started a new project but this still happens.
This happened to me too a few times..Very annoying. Nothing works. I have to start over.
I changed some AI files and they automatically reloaded into AE, like they do.
I hid all the layers(with the eye icon) and then turned them on 1 by 1. Some layers were visual, but some(AI) layers weren't. So I think maybe it's because I changed the AI file some things got messed up.
Sorry for your issue.
Could you share more details:
Here's what you could try:
Go to After Effects Preferences > Display > uncheck "Hardware Accelerated Composition, Layer, and Footage Panels"
Let us know how it goes.