Make sure you have enabled developer mode on the phone, the phone must be plugged in to the VM (In VirtualBox: Devices -> USB -> {phone}) and that the screen is unlocked.
On the phone you should see a "USB debugging connected" notification when it's plugged in.
If the phone is properly connected, you'll see it in Android Studio in a number of places, including the LogCat and right at the top of the screen in a little dropdown to the left of the run button.
Lastly, you can run the app manually and then connect the debugger if you want. Just run the app on the phone, then click the little icon in the top right with the green bug with an arrow over it.
I made a sample app that just says hello world with kivy and I am trying to put it on an android tablet I bought.
I used a virtual machine (Virtual box) and use bulldozer to loaded to the tablet. However when I run it the terminal just prints in a loop
#waiting for the application to start
any idea on what could be the problem, or how can I start the application
kivy app in adroid with buildozer, terminal loops on "#waiting for application to start"