One of your posts triggered our automod, and it gave you an instance ban from sh.itjust.works. When a user is instance banned they also get banned from every community they have interacted with on that instance. Or at least that's how Lemmy worked at that time; we have since upgraded and I don't know if the behavior had changed.
Upon review, the automod action was clearly a false positive. You were unbanned, which unbanned you from all of those communities.