MMS Messages not sending or receiving on Group Texts

XM's size limit for MMS is a meager 600kb versus Verizon's limit of 1,200kb. You have already figured out that the size limit isn't always enforced when you use WiFi Calling instead of connecting through a cell tower. 

The only workaround is to use a chat (advanced messaging) app such as Samsung Messages, Google Messages or Verizon Messages+, but these only work between users who are signed into or have enabled these Apps. 

@DaveO3  Thanks for the reply.  So are you saying that when I text "hi" to 2 people that the message is over the Xfinity size limit of 600 kb?  I can't even text hi to 2 people at once. 

Brad 

Let's look at possible issues:

1.) When you sent Hi to two people were you sending as SMS or MMS? If you had group text enabled, or when you added a picture or emoji, it would send it as an MMS, if not you would actually be sending two separate SMS. 
2.) SMS is very simple, is unlimited, is free/included, and does not require that you have cellular data turned on. MMS is more complicated, requires cellular data be enabled, gets charged as data, AND once it gets messed up because of size limits or something else they can clog up and not work for days at a time. UGLY. Not good news. 

@DaveO3 Yes, group chat is enabled.  I create a new conversation, add two people at the top.  When I type "hi" it says MMS blow the send arrow.  I hit send and it spins forever until it decides to stop.  I am trying to figure out why my brand new Samsung S20 Ultra cannot send these simple MMS messages.  Seems weird that it doesn't send.  I have read a lot of forums online where people have had the same problem as me, but in March, April of this year.  I have updated all apps and the actual phone.  But nothing seems to be working.  I apprecaite any help and advise.  The weird thing is I can send MMS messages to 1 person, just not a group.

Thanks,

Brad

Last night I went to the Xfinity store and they tried for 2 hours to fix my problem.  They were with Samsung support for a while.  They started my phone in safe mode and the MMS messaging worked for around an hour, then stopped again.  This is a big problem I have.  It works for some unknown reason for an hour then stops for 5-6 hours.  I don't change any settings inbetween it working and it stopping.  I can do the work around (wifi calling, airplane mode, wifi on) and get messages right away.  Also the weird thing is when someone sends me an MMS group message I get a notification at the top of my phone with the person's name AND THEIR REPLY, but that disappears after a second.  When I go to my texting app it wants me to click the download and it just spins.  I have used the default texting app, Google Messaging, and Message+ all with the same results.  Anyone have an idea?  I have turned my phone on and off many times, reset network connections, and done just about everything I've seen online.  I am starting to think the S20 Ultra just can't do MMS all the time and it is Samsung's fault.

I think that the problem is with the Samsung Message software and may also relate to the settings on your S20. Remember, SMS and MMS rely on your carrier's servers, whereas Samsung, Google, and other advanced messaging (aka Chat, or RCS in the Android world) rely on Samsung, Google, and other non-carrier servers. MMS is not chat, but it does allow group texts and pictures between almost all carriers and devices subject to various size limits. 

Do you have Chat enabled in your message settings? If so, turn it off and see if you have better luck. 

Also, if you ever enabled Chat on any other platform such as Google Messages,  Verizon Messages+, or Apple iMessage you need to remove your phone number from them as anyone logged into any of them will have trouble texting you. 

I have a similar problem on my iPhone 11 Pro. I can receive messages from groups, but not send them. The message hangs and then I get an error that says "message failed to send." It is really aggravating, and I've never been able to find a solution. This is the same whether on messages for the phone or mac, whether I start conversations from my phone number or email address (an option in Messages). The group MMS contains a mix of iPhones and Androids. I can text them individually, but not in the group.

Give this a try: For the Android receipients, make sure their phone numbers start with +1 (xxx) xxx-xxxx

i found a simple solution. There is a toggle to turn on/off the ability to send MMS when mobile data is turned off. I was on a Motorola moto g

Same issue here. Xfinity is trash. Their customer service for mobile is somehow even worse than their cable/internet customer service. Can’t wait until my phone is paid off so I can go back to Verizon. I don’t care if Verizon is double the price. I just want a phone that works!  What a scam!