@Ozzboy 

Hi, could you please help me check whether I got it correctly:

Currently, both the Epson printer and MacBook are connected to the Wi-Fi network successfully, but when you try to add the printer on MAC for air-print, MAC is unable to locate the printer?

If yes, I used to see several similar cases:

Case one: Deco X60+HP printer

Solution: I have an HP Office Jet - and apparently HP turns off Internet Printing Protocol (IPP) by default. I went in through the printers web interface - in the case of this HP, it was in the NETWORKING tab, ADVANCED, Internet Printing Protocol. I ticked the Enable IPP box and voila - the printer shows up in the AirPrint dialog and prints as expected.

Your error is very close to this one and maybe you could check whether you have such an option on Epson.

Case two: Deco M5 with an unknown printer

Solution: I had assigned my printer a static IP address. When I went thru the setup wizard on the printer, it found my new deco wireless network, prompted me for the password, and then would say success, connected. But in reality, it wasn't fully on the network.  Windows could see it, but couldn't complete installing it as a device.  It would fail every time, and iOS devices couldn’t see it at all. Once I discovered the printer was still set for a static IP address, I changed it over to the dynamic, and now DECO announces a new device has been added to the network.

@Ozzboy 

Thanks for getting back to me.

In this way, I think the printer might not be successfully connected to the Wi-Fi yet.

If you check on the online list of Deco, will you be able to see the Epson printer here?

(A small notice, since you used other routers before Deco, in case you might set up static IP on the printer, could you please check whether the printer is set to DHCP/dynamic IP?)

I see the printer is capable of Ethernet connection, so I wonder if you are able to link it to S4 via Ethernet cable and check whether it could be recognized by Deco.