I just started having the same issue. I used Textra because the Message+ app drained my battery too much and have not had a problem till today. What I can gather is Message+ has an "enhanced group messaging", which isn't clearly called out that it may cause other people issues who don't have Message+. I received a text message from Verizon like you did saying that I had group messages waiting for me, and that I needed to download Message+. I too can't see the group message in a 3rd party app, which likely is meant to be that way by Verizon. If someone else starts a group text outside of that app, then the group message remains to be a standard group message, but something about it being enhanced when made in the Message+ app makes stay inside that app ONLY. Verizon probably just made their app to be like iMessage where only other iMessage people can get them. It will be up to the Verizon app folks to make those enhanced group messages be backwards compatible to non enhanced apps.
Adding a "me too"... I just got this Verizon phone, upgrading from a flip phone, which actually allowed these messages through. I do not wish to use the "Message+" app, but people who send group messages like these from that app are only showing up as these "you have a group message waiting".
Another me too
Was using textra but it stopped clearing read notices after I updated Verizon messages.
Can't get group messages created in Verizon's app, but got the notice text. Verizon seems to be doing an Apple, and trying to get us to use their app
I prefer textra for the customization... Including a dark mode
Lets face it ... the person from Verizon responding to this thread doesn't understand what's going on because they aren't on the USA network.
The other reason they don't know what's going on is the advice to reset things for primary app or reset the phone ... and that makes NO SENSE when we're sending Group Texts out through the Message+ App to people using phones on multiple networks, using older phones, older versions of Apps and ... some of those phones are iPhones that don't have the Message+ App ... yet they still get the texts, pictures and video's we're all sending.
The issue is why does only ONE person not get the texts we're sending. In some Groups that person has an Android phone, in another group that person has an iPhone, and in some mixed Groups a person can receive texts, pictures and videos in one group, but not the other.
Message+ doesn't seem to have an answer, nor do they have the staff who is tech-savy for the American multi-network, multi-phone, system. Another Verizon failure.
I know I sound so negative ... but let's face it ... several months of the same complant spelled out in multiple forums and multiple ways ... and there's no simple answer ... means they don't care.
In the group chats that I created in Messenger +, there is always one or two people who don't get the message. While others on all networks and all types of devices and apps get it just fine. When I open the Group Details, the person who is not getting the messages always has a blue conversation bubble next to their name while those receiving the texts have grayed out convo bubbles. Why is it blue? Cannot find any way to change that and nothing is blocked on either side. Can send a text to these people no problem.