The config files don’t match how i had understood your setup. I though you said the device were using a flexy modem like a FLB 3205 and the wireless network they were connecting to were on the same subnet. It looks like your devices are connecting via the Wired WAN connection. The calls you are making seem to be directed at the VPN IP of the device.
Looking at the error logs it looks like the flexy1 might not even be getting a internet connection.
Can you please provide a backup of the device using ebuddy, with the “include support files” box checked. This will make it significantly easier for me to look over.
Can you provide a clear description of how the devices are configured? How is the LAN setup, what WAN interface is enabled, Is this the interface you are trying to reach with the remote device? Are the WAN interfaces in the same subnet?