Some routers will not immediately pick up the fact that the Edge is routing a secondary address on a WAN port. In order to force this follow these steps:
1) Connect to the Edge via SSH port 2022
2) Select the Ping option
3) Enter 188.8.131.52 as the ping address (or any known Internet address)
4) When asked for the source address, enter the secondary WAN address that you are trying to make work.
5) Select the normal parameters for everything else.
If this ping is successful then you know that the router has ARP'd up the address and that the Edge is configured correctly.