Unable to respond to group chat on iPhone's Messages app

i was abroad so my phone added my email to all my group chats and now that I'm back in the states I haven't had any issues except one group chat. i removed my email from it and I couldn't respond anymore on my phone, only on my computer. i can see all the new messages on my iPhone but I just cant respond. when I add my email back in, it works fine but id love to remove my email and just have my phone number! have tried restarting phone, changing messaging only to my phone number, only to email etc and nothing works

[Re-Titled by Moderator]

Original Title: cant respond to group chat on iphone but can on computer