iMessage ios10 group text keyboard not working

Upgraded to ios10. I have several group messages, but in only one of them I cannot use my keyboard (it doesn't even come up). I can only see a display of the messaging, I cannot send or reply. I also cannot remove myself from the message. I have done, among other things:

Hard reset, toggle imessage off and on (as well as wi-fi and bluetooth), turned off reduce motion, accessed the keyboard in other messages and apps, reset network settings.