I need a little help.
I have a web page that worked for about a year and suddenly In Chrome and Opera the full screen video stopped working. I have not made any changes to it since I published it, and I don't think I've made any changes to it. but hey, it's been a year so, maybe. Funny thing is, I have some a duplicate and some almost duplicates deeper in the website that appear (to me) to be have the exact same code and work just fine.

Doesn't work:
http://texxsmith.net/soon

Works:
http://texxsmith.net/soon/Video_WildGrass.html

Since both Chrome and Opera use the same engine and changes happen there, you have to dig into your code.
I didn't but want to mention that I check out my code and two sites to see if there's any mention of troubles.
https://caniuse.com/ and https://validator.w3.org/