1. The User is not standing on the smart scale for sufficient time. User need to stand on smartscale about 15 sec. 

2.  Legs might be dry completely so moisten your legs little before measuring. 

3. Floor is not flat and hard or smart scale is kept on carpet or other soft surfaces. If your weight is not balanced evenly on the smartscale. Smartscale will refuse to connect. 
4. The User is wearing socks or shoes while weighing himself / herself.
5. Your Battery might be about to die. Kindly change them.