Can't seem to subscribe from a new instance...

Hey guys, I've set up an instance for myself and some friends on https://halubilo.social but whenever I tried to subscribe to a lemmy.ml or lemmy.world community I get this:

Target server https://lemmy.world/inbox rejected https://halubilo.social/activities/follow/200f3fb9-7d98-4172-badb-5ce38dc2de81, aborting
Target server https://lemmy.ml/inbox rejected https://halubilo.social/activities/follow/f3eb39bd-0b8d-4a92-b800-7968fa7e9af4

Is there some set up I'm missing out on on my end?