Straight Talk Samsung Galaxy S6 Can't receive MMS group messages but can receive personal MMS

[Christy B1]

Hey! I just got a new unlocked Samsung Galaxy S6. I set up my APN setting and am getting LTE right now. I am able to receive photos when set from one person but can't receive any group mms messages even though I can send them. I get the download box but it won't download. I don't know what to do, I don't know what kind of issue this is, if it's APN related or just some setting issue. This phone is more complicated that I thought.
Thanks in advance