I have theories as to how to catch the remaining Pokemon.
Unown A - Bring Unown !, Unown ? and another Unown as Support and get a flawlessly catch the previous Pokemon(I literally can't tell which PKMN) with one of the Unown to unlock Unown A.
Masquerain - Defeat Surskit flawlessly with either a Water-type of a Flying-type, since Surskit is Water-type and Masquerain is the latter type.
Castform - Bring either a Fire-type, Water-type, Ice-type or Normal-type and defeat Smeargle flawlessly with it. I guess Castform will appear with the corresponding form (Fire-type=Sunny Form).
Reuniclus - Bring Solosis and Duosion (and Gothitelle) as support and defeat Gothitelle flawlessly with one of the mentioned Psychic-types to unlock Reuniclus.
It's most likely you tried these methods, but if you haven't, take a shot. I mean the worst that can happen is that it doesn't work.
Unown A - Bring Unown !, Unown ? and another Unown as Support and get a flawlessly catch the previous Pokemon(I literally can't tell which PKMN) with one of the Unown to unlock Unown A.
Masquerain - Defeat Surskit flawlessly with either a Water-type of a Flying-type, since Surskit is Water-type and Masquerain is the latter type.
Castform - Bring either a Fire-type, Water-type, Ice-type or Normal-type and defeat Smeargle flawlessly with it. I guess Castform will appear with the corresponding form (Fire-type=Sunny Form).
Reuniclus - Bring Solosis and Duosion (and Gothitelle) as support and defeat Gothitelle flawlessly with one of the mentioned Psychic-types to unlock Reuniclus.
It's most likely you tried these methods, but if you haven't, take a shot. I mean the worst that can happen is that it doesn't work.