1. Make sure you have connected your phone to pc with usb cable for data transfer

2. Make sure usb debugging on your android phone is turned on 

(IF NOT go to settings -> about phone -> build number and tap it many times 

(like 10) until you see message "you have enabled dev tools". Then go back to 

settings and search for "usb debugging" and turn in on.

3. Instead of running "expo start" in terminal type "expo start --localhost --android" and hit enter

​

try:

expo start --localhost --android