Ambiguous: xinjinjumin (Chinese: 新晋居民, meaning: "new resident") is the default username for Lofter accounts, similar to a default Pixiv stacc (user_*), not an actual name. Create your new artist entry with the proper artist name (see help:artists or ask in Danbooru topic #8199 if you need help) and add your posts to that new tag instead.
See xinjinjumin* for a list of artists who are still using the default Lofter username.
