Camera doesn’t work for group calls

Hello, I have an iPhone 6s I am up to date with my software update but for group chat calls I cannot turn my camera on I have tried things in settings but nothing will work. For all except myself and 2 others all iPhone 6s users on my group chat are able to turn off and on their camera but I can’t ,hoping

someone could help

thanks Ps: the FaceTime video logo is grey on my group chat