Hello, my name is Syd and I am with Epson America
Normally this occurs when the generic Microsoft driver for the WP-4020 is installed instead of the Epson driver for the WP-4020. This can happen if the printer is connected USB before the driver is installed, or even USB to a router. The printer should not be connected at all when installing the drivers and only at the 'Now connect the printer' window should the printer be connected. You would want to the following in this order.
1. power off the printer. Do not power on until the end of step 4.
2. go into windows control panel and remove the Epson software (printer driver)
3. restart the computer and verify there are no copies of WP-4020 queue or Epson driver installed.
4. Install the combo printer drivers from the Epson website. Power on the printer ONLY when the install window tells you to do so.
This should ensure when plug/play finds the printer, it will use the newly installed Epson drivers that allows full functions such as tray choice or ink levels.