I would contact Verizon to see if Comcast Home Security is allowable on their system, since it is a competitor's product. If the Comcast home Netgear router is behind the Fios router. That can be the issue. You may have to open ports on the Verizon router, or place the Comcast home router in DMZ mode on the Verizon router.
Verizon tech's can help you with their product. How to place a third party router in DMZ, or open ports on their product.
Verizon tech's can help you with their product. How to place a third party router in DMZ, or open ports on their product.