I am able to install the addon and the download button shows up but it's always grayed out and can't click on it. I am using ot on Firefox on an Android device on Desktop Mode.

I tried everything and it's still not working, there's no such download button.. if someone could help me tho it would be greatly appreciated

This works great for me and deserves praise! It has helped greatly simplify note taking (I parse the output to a markdown file and then pass through an LLM).
The button does exist!! You have to open the video description and click 'Show transcript'. 99% of the time it's there in the Transcript box anyway, and when it's bugged and showing 3 dots a refresh fixes it.