That's not up to Qimage: that's all the printer driver. So make sure you have the latest Windows driver installed from the Epson website. Then make sure your media size is set to something that will fit in the cassette: for example if you have any paper larger than 8.5 x 11 selected, the cassette selections are not valid.
Since the driver is "feeding" Qimage with those selections, you can also just click the "Properties" button and go into the driver and make your selections there; if there is something wrong that won't allow you to select cassette 1 or 2, the driver will tell you.
Regards,
Mike