I don't know if this is a bug, but I'll post it here.
My user ID 1927695782812733440
I purchased Hero's Anthem from Buffbuff and Legendary Hero Pack from Midasbuy. Both transaction were success but I have not received the items in my account.
I've contacted Buffbuff support. I have not received a response but I don't think it's their mistake. So I created a ticket to the game's support. I hope they can resolve this soon because the Hero's Anthem event will end in 1 day.