Group text message says "outgoing" and is sending to each person individually
When I send a message to a group of people, everyone in the group receives it individually and I get their responses individually. The group chat stays there and says "Outgoing" under the photos of the recipients. Some of the recipients have iPhones and some don't.
I have deleted the group chat, deleted each person's individual chat, reset network settings, closed the messages app, tried with iMessages on and off in settings, tried with Send as SMS on and off in settings, and restarted the phone multiple times, but the behavior persists. In other words, the solutions offered in the following places do not work for me.
https://support.apple.com/en-us/HT204065
https://discussions.apple.com/thread/7857347
https://discussions.apple.com/thread/7933912
https://apple.stackexchange.com/questions/74700/problems-with-group-sms
https://www.imobie.com/support/iphone-group-messaging-not-working.htm
What should I try next?
Model name: iPhone 8
Software version: 12.2 (16E227)
Network: Google Fi
iPhone 8, iOS 12