Why can't "com+find"

I Need Help
1

There is a page where text search is not possible with “com + find” in both safari and chrome. Is this normal? Is there a workaround?

https://drive.google.com/file/d/15YQPv7uRz7HR2rRPg8imaXizZTBoJpxC/view?usp=sharing

My site

2

The following 5 pages.↓
It becomes an enlarged image

https://www.sifactory.net/sound-sample.html(無反応)