You’re seeing an Anubis anti-bot Proof-of-Work check to make sure you’re a real...

https://deansinspiringperspective.hexaforgey.com/posts/why-is-proof-of-work-better-than-rate-limiting-for-some-sites

You’re seeing an Anubis anti-bot Proof-of-Work check to make sure you’re a real person and not an automated script. Sometimes this check won’t work if your browser blocks JavaScript. This often happens if you use JShelter or similar tools