I have tried running the application on several mobile phones and emulator and also tried a lot of phone numbers but it shows, "Unable to confirm your phone. Sorry, we are having trouble sending you a confirmation code".
Thanks for posting! There's a couple of different reasons why this can happen from an app rate limit or issues with verifying the number itself. Do you see anything in the Logcat or Console output? If not, can you share some of the numbers and carriers you're having issues with?