help with viber and the origional ipad please

[Ann1]

Hello everyone, i have the origional ipad and i installed the viber app with no problems. I registered my mobile number, was sent a code and all went well for the installatiion. I am ringing some numbers and there is no reply or the app tells me that these people dont have viber installed. Can anyone help me that may be using viber on a similar ipad please. regards ann