I am using Allvoi VOIP service. I can make call through Allvoi phone but all incoming calls are not able to connect.
Call the phone makers support line or your voipo provider. Fios does not support phones outside of their own offerings.
Maybe check the firewall settings and UPnP settings on your router. It's possible that you may need to port forward as well, but let's start off by checking with your VoIP provider first to see what their requirements are.
Many VoIP providers will try to use UPnP to automatically port forward for their services as needed. Sometimes, this is problematic and ou have to port forward by hand. Also, router firewalls with multiple tiers of firewall protection will typically require the Firewall to be set to "Low" at the highest for VoIP traffic to work, unless you make further customizations to the rules.