Bluno Nano MIT App Inventor

I am tried to make android app to control servos using Bluno Nano. I make app in MIT App Inventor. On Android: When I click connect (in polish "Połącz z") i can choose bluetooth device, but when I click device app take lag and Android show error 507. 
Bluno is set to slave and is turn on. In Bluno app communication works fine.
What I do wrong?