Always copy the direct file URL (usually a .mp4, .mkv, or .m3u8) before handing it to the manager. Many sites mask the real link behind a redirect that can break the manager.
Ironically, sometimes the "error" is not a block. If you do manage to access one of these sites, you are bombarded with pop-ups, fake virus alerts, and redirects that break the user experience. Users looking for an "ipagal fix" are often trying to stop their browser from being hijacked by malicious scripts on the site itself.
Governments and local internet providers frequently block access to these domains due to licensing and copyright regulations.