T-Mobile Lumia 640 - Group Text not working

I have received Group Text before, as recent as the 29th of January with 7 other people. I was able to respond to said text as well.

But today, when I try to create and send a Group Text to two other people, my phone says "Can't Send Message, Try Again".
I would appreciate any troubleshooting help with this problem.

I have tried to:
1. Turn on Data and send. Nope.
2. Turn off Data and send. Nope.
3. Turn Phone off and back on and send (data off). Nope.
4. Turn Phone off and back on and send (data on). Nope.

I have Group Text and Auto download MMS On. Am I missing something else that I could try?

Do you have wifi calling enabled/turned on? Sometimes that can mess with something like this.

Thanks for suggestion! Here are the results:
1. Turned off Wi-Fi calling, WiFi on, Data off. Nope.
2. Turned off Wi-Fi calling, WiFi on, Data on. Nope.
3. Turned off Wi-Fi calling, WiFi off, Data on. Nope.
☹