There are pros and cons of this application and ISP providers. Many say that magicJack has issues with AT&T Internet, others say it works great. However, your Internet needs to be very fast to use magicJack. However, in mobile phones magicJack is known to have issues like call drop, connectivity, login issues, force close, etc. It's not a perfect application, but it works. Simply try again or contact the developer using the following email address: support@magicjack.com