This has connected for years. A few weeks ago it starting dropping and required a modem reboot. In the last two days, it will not let me connect at all.
#1 While you are not on FIOS, I point to
https://forums.verizon.com/t5/Fios-Internet/VPN-issues-using-Cisco-AnyConnect-and-FiOS/m-p/560681
which is marked as solved.
#2 If that does not help you:
a) What is the brand and model of your modem?
b) If you have a separate NAT router: What is the brand and model of it?
