I downloaded the proper files from the video-player-with-captions folder. I reproduced your player.
The captions won't work from my Github account (https://peggysuechan.github.io/video-player-with-captions/) nor from files saved on my computer, no from my reproduction of the player in Blogger (https://iandevlinnewest.blogspot.com/).
Perhaps subtitles work from only your Github site.
I downloaded the proper files from the video-player-with-captions folder. I reproduced your player.
The captions won't work from my Github account (https://peggysuechan.github.io/video-player-with-captions/) nor from files saved on my computer, no from my reproduction of the player in Blogger (https://iandevlinnewest.blogspot.com/).
Perhaps subtitles work from only your Github site.