"Ele pertence aqui." was rejected. Not sure why.
It should be (http://michaelis.uol.com.br/moderno/portugues/index.php?lingua=portugues-portugues&palavra=aqui) [def no. 2]
What a great resource this dictionary is. I understand perfectly why "pertence" is wrong in this sentence. Thank you for the link. It will be a great help.
You're welcome. This one, despite being BP, it's vastly superior in content to Priberam, the EP one I talked to you about. The downsides are definitions not being listed vertically and it also doesn't conjugate verbs.
‘Ele pertence aqui.’ is perfectly fine and a lot more natural than the official translation.
Cf. the song Eu Pertenço Aqui from the Portuguese version of Spirit.