Skillshare FAQ: Why Am I Getting A Cloudflare Error At Skillshare?
Cloudflare protects web-servers against Denial of Service attacks. Sometimes Skillshare considers its servers to be under attack and doesn’t show you a page. Unless you’ve tried to access a lot of pages in quick succession, it may be that a potential threat has been flagged for your IP range. These errors go away after a while, but you can also work-around them by opening up the URL you want to visit in an Incognito browser window, or possibly another browser. You can also try removing the “tracking information” from the end of URLs as that sometimes works too.
(update, August 2016, this problem seems to have been fixed)
For many more Skillshare “Frequently Asked Questions”, see the “Unofficial Skillshare Success Blueprint“.