Why is my printer only printing from the rear print tray

REF: https://files.support.epson.com/docid/cp...

The link above is to your user manual. First, I would check the basic print settings. Go to page 86 if you are using Windows or page 109 for OS X, and see what the paper source is set to (Page 89 gives the options and their meanings).

Also, go to page 66, and run through the "Selecting the Paper Settings for Each Source - Control Panel". Here you can change the default paper size for each tray, so when you set the paper source in Windows/OS X to auto, it will know which tray to pull from based on the paper size configured for each tray.