Wow...any of you LG users, try this:
Settings > Language & Input > LG Keyboard > Keyboard height and layout > Keyboard height
Move the height down slightly...this fixed it for me (Text, Facebook, Google Hangouts)
I have an LG V10 (Verizon). After a recent update (VS99023A) that was applied on 7/28/16, I have this same problem. I found that if you change the orientation of the phone from portrait to landscape, you can click Send.