Add participants end-point not adding a contact when a person have never been to the group

[TitoBahe]

That end-point is only working when a person have been to a group, left the group but didnt delete it. So the group shows up on the person's chats page. If that person have never been to the group or deleted it after leaving, its not possible to add him to the group again.
Is it a bug?
Btw, the phone number I was test on has set to "all" who can add him into a new group, I sent a msg on both sides so they would have a conversation before trying to add him and all Logs returned 200:

currentUrl":"http://noweb_1:3000/api/q7BsVdTjhuegG3x6R90u-clientId1/groups/[email protected]/participants/add"}},"data":[{"status":"200","jid":"[email protected]","content":{"tag":"participant","attrs":{"jid":"[email protected]"}

EDIT: After sometime and some more msgs sent, It started working. One friend of mine told me Whatsapp needs sometime to make it work properly.