Hello Seantyler11,
Thanks for asking the Apple Support Communities about the screen rotation. This help article: If the screen doesn‘t rotate on your iPhone, iPad, or iPod touch states:
Thanks for asking the Apple Support Communities about the screen rotation. This help article: If the screen doesn‘t rotate on your iPhone, iPad, or iPod touch states:
Some apps don't rotate. Some might use only portrait or landscape mode, or switch depending on the content.
The YouTube app must be one that only rotates based on the content, the videos. Since the screen rotates while watching a video, this shows that the iPhone and the screen rotate function are operating as expected. Thanks again and have a great rest of your day.