Hello in the start of this event i dont have all 5 pokes. I have 4 except raticate alolan. Help me please!

This is not a bug. You didnt recruit the Rattata-Alolan in the dark realm during the quest there.

You have to go back to the Dark Realm and recruit all the pokemon there so you can use them on the battlefield on the quest later on.

Yeah but can i go? because i have completed this quest and catch darkrai, too

Yes you can. You have to beat the Horon boss north of Necropolis without one of your pokemon fainting during the fight. Doing that will respawn Alucard in his castle on the third floor, fight him while having a pokemon with the move Miracle Eye on your team and you can go back to the Dark Realm.

Thanks a lot!!!