I just created an animated subscriber alert for twitch wich needs to be transparent. I rendered it as a quicktime in RGB + Alpha. When i open the new file again and put it above an image or video it is perfectly fine and transparent but when i open it in Streamlabs or OBS it has a black background to it. How do i get rid of that background?
Transparency is a matter of interpretation. You may need to enable some option or use a different media format/ CoDec. Not sure what OBS at al currently want. I don't keep up with this stuff. Apparently at some point they only wanted WebM and even that didn't work right a lot of times...
The whole process from rendering format and codec to encoding software to media player must be compatible. There are specific requirements for each step. Foul up any one of them and the process will not work. For most Web-Based distribution of animated graphics files using After Effects instead of a web app like Adobe Animate is a lot like driving screws with a hammer. You might get the job done eventually but it isn't going to be as pretty as it would be if you used the right tools in the first place.
Check the workflow recommendations for the software you are using to generate the final product then follow them precisely. If you are still having problems, give us the details and share any appropriate links so we can try and help.