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None of my contacts appear in my Viber contact list
Make sure that you have a strong Wi-Fi, 3G or 4G connection. Viber will only sync when there is an adequate internet connection
Make sure the contacts you expect to see in your Viber contact list are Viber users. If they are not Viber users, they will not appear in the Viber contact list.
Refresh the Viber contact list by pulling the screen down and releasing
Check your device settings for which contacts to display. Select "All contacts" in order for Viber to recognize all of your contacts (on iPhone, go to Settings > Mail, Contacts, Calendars > Import SIM contacts)
From your device contact list, remove a contact you know for sure is a Viber user > Add them back to your device contact list > Check your Viber contact list to see if the sync has occurred
Some Android devices require that your contacts are synced to your Google account before being able to sync them to Viber*
Restart your device
If none of the above solves the ...••••• Uninstall Viber and re-install••••