@stephenw10 The original pfsense device had multiple IP addresses on the WAN interface. When I migrated to the SG-3100, rather that using the primary public IP address, it was using one of the other IP addresses on the WAN interface. Once I realized this, I modified the WAN interface, then the clients were able to connect again.
The SG-3100 in now in place and all is well.
Thanks for your assistance.