Help adding a person to a group text when the add sign does not come up

Is there an android phone in the chat? if there is, you usually can't add more people. just make a new chat with all the same people, and the person you want to add.

If you read the response just above yours, if there is someone in the group text already that is a non-iOS user, you cannot add or delete anyone from the group.

You're welcome. Unfortunately, you cannot add or delete any additional users.

Hwo do i add a person to a group text, when the add a person message does not come up on the phone?

thank you, 2 of the group are non iphone users.