Hey
I assume it was all AOK with the previous modem gateway (Was it a TGN797v3?) if so, use that instead of the TGN799MAX and see if it works. The TGN797v3 has a WAN port just the same as the MAX.
Since it's an Epson, It might need to have a reset done, or go through the USB configuration to get the Wifi working again.
Can you connect the Apple Laptop via thernet, then a USB cable from the laptop to the Epson?
I don't have an epson so I cannot go through it all, but it's pretty much the same as my Canon or my Samsung. Both have the simplest option of using a USB cable to do the intial configuration, after which you disconnect the USB cable and it connects via WiFi.
This video might help.
For the Apple, I have no idea. I have a Mac Mini, so I might be able to help. What version of the OS do you have?