Lemmy world is under persistent denial of service attack in recent weeks: https://lemmy.world/post/2923697

The admins are aware and responding daily, the technical specifics of the attack keep changing as they close off one avenue of attack, the attackers switch to a slightly different approach in a game of cat and mouse.

There's nothing you can do but wait, it will come back online... or use alts on other instances. Lemmy world has a competent admin team who is working hard to weather these attacks, but lemmy the software is not prepared for this kind of adversarial resource consumption so it's a very hard job to both layer protections on top of lemmy and also to fix underlying issues so it's natively more resilient.