The list of people you’ve connected with or invited through the GroupMe app.
Hi Harry,
Thank you for reaching us, Regarding your concern Using the GroupME Web App Adding a member to a Group is possible but sending them an SMS text using GroupMe web app are not allowed aside from chat and file sharing.
If ever you unable to add a new member to your Group using GroupMe web app. The member might shown as not allowed or nothing will happened.
Please check this article regarding unable to add someone to you Group in GroupMe
Alternative way to add a member to your group by just giving them a sharelink or QR code via email, text or Social Media.
To get the QR code or Share link from your Group. On your GroupMe click on the Group profile picture. Turn Enable Group Sharing on. Copy the Group sharing link or QR Code and share this to the member you want to add via email, text or Social Media.
You can also check this article regarding why you got the error when adding a member and how to add member via sharelink or QR code
I hope this answer is helpful, if you have further questions, feel free to reply back.
Regards
Jansher