Oomesh, thank you for your response. I have downloaded the Airbnb app on my phone. I realize now, that perhaps the reason why it would not accept my cell phone number is because it's a Tracfone (prepaid) cell phone. I've had for years now but I am assuming that Airbnb does not consider it a legit mobile number. 😞
But that is okay. I can still use the App on my phone to access Airbnb notifications and/or messages from rental owners. So all is good.
Again, thank you for your response!