Exporting Premiere Pro video with no background?

Hi everyone! Basically, I created a 15 second long animation in After Effects and exported it from there with a transparent background, no problem. I'm not great with AE so after that I put it in a Premiere Pro project and changed the speed and size of the images a bit. I've been trying to export it from there for the last few days and it's not really working properly. The end goal is to have it on the front page of my Wordpress blog if that makes a difference.

To export it, I've been using Quicktime format (I'm on a Mac) and selecting PNG from the menu and also tried Animation later on. And then choosing 32 from the depth menu every time.

It exports alright on my Mac and I can watch it back but suddenly when I even try to upload it to OneDrive, Dropbox, etc. myself and others can't watch it back. It'll say things like "Sorry, there was a problem loading the video" every time, it doesn't even show a thumbnail which makes me think it isn't even fully uploading? It won't even load if it's sent over email. I'm a beginner so this is all very confusing to me.

If anyone has any tips or tricks that I'm missing, I'd really appreciate it!

Thanks so much.