I can't print double sided with my Epson Printer

Try this...

Instead of Layout select Printer Features from that drop down menu. Now scroll down that feature list until you see the 2-sided Printing option. Turn it on and then select either long edge or short edge binding. If you want the option to stay on then you must save it as a setting. I have an Epson WF-2860 and this is how it works for me.

I have noticed that the two-sided settings can be different depending on which application you are printing from, Word or Safari for example.