Viber@Android: existing Viber contacts not shown in the contact list

Recently some of my friends reported this problem - after they changed their phones, and installed a fresh copy of Viber on android, existing Viber users in their contact list did not feature in the Viber Contacts if the app.

Upon looking up the net I found that this is a known problem with Viber :

Here are the steps to solve the problem:

1.     Try tapping on the 'More' tab at the bottom of the Viber app, then select "Settings" and the add a check mark [√]  to "Show all Contacts"

2.     If you do not see someone in your contact list whom you know to have Viber, it might be that the list is not updated (this may be due to an unstable connection during setup, or just a slight delay). To update your contact list, re-sync it by re-initiating Viber or by manually updating your contacts list.

3.     If this does not work, send the user an invite and if the number is a registered Viber user, it will automatically update the Viber contact list.

Enter into your Viber contact list, then select the device's menu button, and tap on "update contacts". Then just click your device 'home' button. Viber will run in the background. In about 30 min. to an hour, check again by clicking on the Viber icon.

4.     Dial a existing Viber user's number manually, using the Viber keypad

      The phone number format should include the plus sign, country code, cell code and phone number. The standard format is: +(country code)-(cell code)-(phone number).For example: +1-555-555-5555

5.     Last but not least, do ensure that you have an active Internet connection

 Hope this helps.

Further reference
Android: Contact list is not showing your friends as Viber users?
Why Viber fails to recognize my contacts as Viber users?