If a person has left the group in the past, you need to be in their Telegram contacts to add them back.
They can still join via an invite link as long as they are not on the group's invite link as long as they are not on the Removed Users list.
194
抱歉，此使用者自己離開了群組，您無法將他加回
22/194
初音 ミク,
Dec 19, 2018 at 12:53