Originally Posted by ankur.dubey
Using nexus 4.
Navigation buttons have disappeared after a reboot. Expanded desktop mode is off. Using pie controls for the time being. Please help
Sent from my Nexus 4 using XDA Premium 4 mobile app
search for a program that enables and disables buttons. i found such programs when i had the same problem. as far as i remember there is also a file you can edit for disabling enabling the buttons.
for me none of that worked and i had to reinstall android!
Sorry but i don't remember the specific instructions or programs to guide you but i hope i helped a little.
edit: i found in my bookmarks a video that might help you