https://lemmy.world/c/hardcore@lemmy.ml (It’s a music style community): 404: couldnt_find_community
Other communities work fine: https://lemmy.world/c/linux@lemmy.ml
Do I have to enable my community to be federated or is it maybe getting blocked due to the name?
You need so search for it (!hardcore@lemmy.ml) on your instance (lenny.world). The search won’t yield any results but will trigger a request to lemmy.ml and it should become accessible / appear in searches a moment later.