If you're seeing this on your phone while trying to access the desktop site:
Your ISP or local network (school/work) might be blocking specific YouTube subdomains or desktop redirects. If you're seeing this on your phone while
Using an old version of Chrome, Safari, or the YouTube app can lead to compatibility errors with modern web protocols. Step-by-Step Fixes for Mobile Users causing a "Webpage not available" crash.
Stored data from previous sessions can prevent the page from loading correctly. If you're seeing this on your phone while
The browser is trying to force the desktop version ( app=desktop ) while the YouTube app is trying to pull you back to the mobile interface, causing a "Webpage not available" crash.