For the LG G6 I solved this by going to Settings/Display/Home touch Buttons and slid the Instagram slider to the left to turn of the home touch buttons within Instagram. This allowed the text box to be seen above the keyboard.
Also I would like to add that, on my LG G4, wi-fi on, data off = no MMS. wi-fi off and data off = no MMS, data on and wi-fi in both its states = MMS.
For some reason my LG G4 requires Data to be on, that really and truly sucks
I know it's an old post but I'll jump all over this and say that I did not need to have my data enabled when sending and receiving MMS messages while using my Windows based Nokia Lumia 920 on the Bell Canada mobile network. My Data was always switched to off because I am not on a plan and using...